claims depot shelf
High-Temperature Superconductivity
Formal claims (Lean)
-
Starting from the t-J Hamiltonian of a single mixD ladder (intra-leg tunnelling tx, strong spin exchange Jy between legs, no inter-leg tunnelling), the paper constructs a 2D bilayer by stacking ladders and coupling them with a small tunnelling tz. The MPS+MF approximation replaces the stack by one ladder subject to self-consistent pairing and hopping mean fields, and from the converged effective H
-
The paper's central claim is that the temperature dependence of the BSCCO-induced NV relaxation rate $\Gamma_1(T)$ at zero field is a direct readout of three distinct low-energy dynamical regimes in a thin-film cuprate. At $T \ll T_c$, $\Gamma_1 \propto T^2$, consistent with nodal d-wave quasiparticles at BCS mean-field level. Near $T_c \approx 90$ K, $\Gamma_1$ rises in a sharp symmetric peak tha
-
The paper's central claim is that the temperature dependence of the BSCCO-induced NV relaxation rate $\Gamma_1(T)$ at zero field is a direct readout of three distinct low-energy dynamical regimes in a thin-film cuprate. At $T \ll T_c$, $\Gamma_1 \propto T^2$, consistent with nodal d-wave quasiparticles at BCS mean-field level. Near $T_c \approx 90$ K, $\Gamma_1$ rises in a sharp symmetric peak tha
Stated claims
-
The central claim is that magnetoconductance (MC) across the superconducting transition in sputtered BSCCO thin films is dominated by superconducting fluctuations (SF) and, closer to the transition, by vortex dynamics, with weak antilocalization (WAL) playing at most a subordinate role in a narrow temperature window. The evidence is a series of low-field MC cusps whose interpretation changes with temperature: in the 82–90 K window (sample B08D) the cusp is well described by the Hikami–Larkin–Nagaoka (HLN) form with prefactor $\alpha'$ below unity (0.85 at 82 K, 0.15 at 90 K); in the 68–78 K window the cusp reaches millisiemens magnitude and is fit by the Aslamazov–Larkin plus Maki–Thompson model with a dephasing time $\tau_\phi$ of $4\times10^{-11}$ to $4\times10^{-10}$ s and a diffusion constant constrained by cuprate upper critical fields of 50–150 T; and near 80 K neither model alone works, which the paper reads as a coexistence crossover. The same ordering — a WAL-like window above an SF window — is reported for a second film in the Supporting Information, with the windows shifted. Quasi-two-dimensional, pairing-dominated physics is established independently through the Berezinskii–Kosterlitz–Thouless (BKT) analysis: the extracted $I$–$V$ exponent $\alpha = 3$ crosses at 66.06 K and the Halperin–Nelson fit yields $T_{\mathrm{BKT}} = 66.85$ K for sample B18, with the small difference attributed to different vortex-excitation pathways in the two measurement protocols. The Hall resistance reverses sign near the transition, and a non-superconducting control film shows no WAL-like cusp, which the authors take as evidence that the feature arises only in conjunction with superconducting correlations.
-
The paper establishes that the metallic covalent bonds in M(BN)5 clathrate superconductors exhibit anomalously high sensitivity to the choice of exchange-correlation functional, distinguishing them from conventional metallic-bond-mediated superconductors. The PBE functional, through its over-response to density gradients, expands lattices by about 2% relative to PBEsol, leading to underestimated interatomic force constants, phonon softening, overestimated electron-phonon coupling, and, crucially, Peierls instability manifested as imaginary phonon modes. In contrast, PBEsol—with its smaller exchange enhancement factor μ and correlation parameter β—produces tighter lattices, harder phonons, and wider electronic bands near the Fermi level, suppressing Peierls distortion while retaining strong coupling. Using PBEsol, the authors predict that Rb(BN)5 and K(BN)5 are dynamically stable and have superconducting critical temperatures of 113 K (and 138 K at 2 GPa) and 102 K, respectively, both of which were missed by previous PBE-based screenings because PBE produced imaginary frequencies.
-
The central claim is that two dynamically stable phases of NaH6—cubic Pm-3m and rhombohedral R-3m—host high superconducting transition temperatures at moderate megabar pressures, despite containing well-defined H2-like units with elongated H–H bonds. The cubic phase reaches Tc = 230 K at 50 GPa, while the rhombohedral phase shows a strongly pressure-dependent Tc that climbs from 34 K at 10 GPa to 157 K at 90 GPa. Mode-resolved electron–phonon coupling calculations reveal that Raman-active hydrogen vibrations dominate the coupling, and their linewidths increase with the tilt angle of the H2 units. A symmetry-based model of the change in the hydrogen sublattice's second-moment tensor under vibration shows that the in-plane tensor components perpendicular to the threefold axis grow with tilt, consistent with the observed trends in Tc and linewidths. The paper thus presents NaH6 as an unusual molecular-like hydride in which hydrogen-sublattice organization, rather than its suppression, enables high Tc.
-
On the paper's own terms, the discovery is that the tilt-free phase of La$_3$Ni$_2$O$_7$ is a genuinely different electronic state of the bilayer nickel sector, not merely a symmetric version of the same metal. Differential optical conductivity shows a broadband transfer of spectral weight from 1–3 eV excitations toward below 1 eV, with the low-energy gain of $\Delta K_{int}$ stepping up markedly across $T_{st}$ while the high-energy loss is only partially compensated within the measured range. Raman tilt-shear modes (2) and (3) vanish between 543 and 545 K while acquiring Fano asymmetry, tying the electronic changes to the lattice. A Drude–Lorentz decomposition attributes the largest low-energy gain to L2 (about fivefold) and L3 (about twofold), whose resonance frequencies, plasma frequencies and linewidths converge to identical values above $T_{st}$. The authors interpret the L2/L3 merging as the degeneracy of the two antibonding $3d_{z^2}$ branches in the higher-symmetry structure, and the simultaneous hardening of L1 as an increased splitting of the bonding branches, with the Fermi level sitting between them — a level scheme that differs from published DFT+U calculations, as the paper acknowledges when it notes that pressure and temperature drive opposite electronic changes in the same nominal crystal structure. The conclusion is that the tilt-free transition reconfigures the $3d_{z^2}$ orbital sector — the interlayer-coupling degrees of freedom that orbital-selective theories tie to interlayer pairing and superconductivity.
-
The central claim, on the paper's own terms, is that the t-J(-U) model provides a good description of the principal properties of the high-Tc cuprates, including their dynamic paramagnon and plasmon excitations. The argument runs from the Hubbard model in the regime $U \gg |t|$, through a canonical transformation that removes the mixing with doubly occupied sites and yields an effective Hamiltonian of projected hopping plus kinetic exchange $J = 2t^2/U$, to the recognition that this exchange term is exactly a singlet-pairing term: the local pair operator $\hat{B}^\dagger_{ij} = \frac{1}{\sqrt{2}}(\hat{b}^\dagger_{i\uparrow}\hat{b}^\dagger_{j\downarrow} - \hat{b}^\dagger_{i\downarrow}\hat{b}^\dagger_{j\uparrow})$ rewrites the spin correlations as pair hopping, so that real-space singlet pairing and spin-density order are competing faces of the same term. On this basis the model yields a single phase diagram containing d-wave superconductivity, coexisting pair-density-wave order, a nematic phase, and the Mott transition.
-
The paper claims that a simple two-step process—extended dry grinding of bulk pyrolytic graphite followed by air annealing at 670 K—generates high-density, nearly parallel wrinkle arrays on the basal planes of graphite nanoflakes. TEM imaging enhanced by 2D-FFT filtering reveals these wrinkles, while magnetization measurements show a vertical shift in field-cooled hysteresis loops that is unambiguously attributed to trapped magnetic flux (not exchange bias). The trapped moment persists above 390 K, and its sign is controlled by the cooling field direction. The correlation is exclusive: only the air-annealed sample bearing wrinkle networks exhibits flux trapping, whereas unannealed and vacuum-annealed controls do not. This is presented as evidence that wrinkled regions host granular high-temperature superconductivity.
-
The central claim, stated on the paper's own terms, is that no axion dark matter signal hides in the $15.30\text{--}15.85\,\mu\mathrm{eV}$ mass range above couplings of about $1.3\times$ the KSVZ benchmark, and that reaching this sensitivity required solving the electrodynamic problem that had kept high-temperature superconducting haloscopes from being tunable. An off-axis tuning rod breaks the azimuthal symmetry of the $\mathrm{TM}_{010}$ mode, driving transverse currents across the tape-assembly seams and exciting cutoff-free TEM radiation that drains the stored microwave power; the authors eliminate this channel by soldering substrate-stripped rare-earth barium copper oxide (REBCO) tapes with their copper stabilizer backing directly onto the copper shell, establishing full electrical continuity across every seam. In an $8\,\mathrm{T}$ field the cavity then tracks its $\mathrm{TM}_{010}$ mode across $3.21\text{--}4.05\,\mathrm{GHz}$ at an unloaded quality factor near $2\times10^5$, three to four times a copper cavity's, and with a near-quantum-noise Josephson parametric amplifier reading out at about $280\,\mathrm{mK}$ the system scanned $133\,\mathrm{MHz}$ at $1.28\,\mathrm{MHz/day}$. Twenty-one candidate clusters were rescanned and all were statistical fluctuations. The resulting 90% confidence exclusion reaches $1.3\times$ the KSVZ benchmark in a Frequentist analysis and the KSVZ line itself in a complementary Bayesian analysis, a factor-of-60 improvement over earlier direct limits in this band.
-
The central claim is that the electronic structure of these artificial high-$T_c$ superlattices is tuned by the geometric ratio $L/d$ in exactly the way the BPV framework predicts, and that four independent X-ray observables track that tuning through the superconducting dome. The chemical potential, read from La 3d core-level binding energies, moves monotonically with effective doping and sits above the BPV-calculated bottom energy $E_L$ of the second subband for $L/d$ = 0.67 and 0.78, the samples nearest the dome's maximum, indicating that the second subband is occupied there but not at $L/d$ = 0.44. Fermi-Dirac fits to the valence-band leading edge place the $L/d$ = 0.67 spectrum closest to the Fermi level, signaling enhanced density of states; Cu 2p spectra show the Zhang-Rice-singlet-like screening shoulder (the final state in which a ligand hole screens the core hole) strongest, and the poorly screened satellite weakest, at intermediate $L/d$; and X-ray linear dichroism finds in-plane $d_{x^2-y^2}$ orbital weight of about 87% at $L/d$ = 0.67 and 77% at 0.78. The authors take the systematic correlation of all four features with the dome — including its asymmetric Fano-like shape with the maximum offset toward lower doping — as direct spectroscopic support for confinement-induced electronic reconstruction near a Lifshitz van Hove transition that enables Fano-Feshbach resonant pairing.
-
The paper establishes that heavily Sr-doped La2SrNi2O7−δ (nominal composition, with measured La:Sr ≈ 1.86:1.14) crystallizes in the tetragonal space group I4/mmm at ambient pressure, with no octahedral tilting and a Ni–O–Ni bond angle of 180°. This is the same symmetry observed in the high-pressure superconducting phase of the parent compound La3Ni2O7 and in compressively strained films that superconduct at ambient pressure. Despite sharing these structural features and showing metallic transport without density waves, the material does not become superconducting under any tested condition. DFT calculations using virtual crystal approximation and PBE+U (U = 3.5 eV) indicate that Sr doping primarily adds holes to the Ni-3d_z2 orbital, reducing its electron occupation to 0.92 (compared to ~1.5 in La3Ni2O7) and creating a large, nested-unfavorable γ Fermi pocket. The central claim is that this severe departure from half-filling of the dz2 band suppresses the interlayer superexchange coupling that would otherwise enable high-temperature superconductivity.
-
The central claim is that high-temperature unconventional superconductors are not scattered through materials space but concentrate in one characteristic region, primarily controlled by a large average deviation of electronegativity and an intermediate mean number of valence electrons. The argument runs through two independent routes: an unsupervised principal component analysis of the full 147-dimensional representation, computed without any transition-temperature information, places cuprate, iron-based, and nickelate families in overlapping parts of the same pocket, while a supervised gradient-boosted model trained to predict transition temperatures achieves a mean absolute error of 3.28 K and a coefficient of determination of 0.931 and ranks the same two descriptors at the top. The paper also shows the trend is systematic: the upper envelope of observed transition temperatures rises with electronegativity deviation, including within iron-based subfamilies, and the highest transition temperatures appear for mean valence-electron counts near 7 to 8. It presents the resulting region as an empirical materials-space prior for screening rather than as a microscopic theory of pairing.
-
The authors claim that the Fe‑Se‑H compound, obtained by thermally diffusing hydrogen into a FeSe single crystal, is a type‑II superconductor with a critical temperature exceeding 295 K at normal atmospheric pressure. They base this on the non‑resonant EPR signal being U‑shaped in fields up to 6000 Oe at 295 K (the same shape as the pristine FeSe superconductor below its 8 K Tc) and on the appearance of quasi‑periodic oscillations with a period ≈20 Oe, which they attribute to the magnetic‑flux quantization of individual Abrikosov vortices. The period matches a calculation using the known London penetration depth of FeSe at a reduced temperature T/Tc ≈ 0.87, from which they infer Tc ≈ 340 K and a zero‑temperature energy gap of about 54 meV.
-
Starting from the t-J Hamiltonian of a single mixD ladder (intra-leg tunnelling tx, strong spin exchange Jy between legs, no inter-leg tunnelling), the paper constructs a 2D bilayer by stacking ladders and coupling them with a small tunnelling tz. The MPS+MF approximation replaces the stack by one ladder subject to self-consistent pairing and hopping mean fields, and from the converged effective Hamiltonian yields the gap Δ between the ground and first excited state. The critical temperature is Tc = Δ/R(Kc), with Kc the Tomonaga-Luttinger parameter of the isolated ladder and R(Kc) the ratio function of Ref. [19]. For tx=0.7Jy and tz=0.2Jy, the paper obtains Tc between roughly 0.1 and 0.5Jy across densities, and states that, once implemented, these systems would realize analogues of repulsively mediated high-Tc superconducting states, subject to three explicit caveats: competing many-body instabilities are not ruled out; the entropy per particle (the practical figure of merit in ultracold gases) is not computed; and the mean-field step makes the Tc values overestimates by a factor earlier work places near four.
-
The central claim is that cubic YH10, long predicted to superconduct at or above room temperature, would instead have a critical temperature of roughly 260–270 K at 250 GPa. The argument runs through anharmonic phonon renormalization: the stochastic self-consistent harmonic approximation stabilizes the soft hydrogen vibrations, opens a phonon gap near 50–100 meV, and reduces the electron-phonon coupling from about 3.3 to 2.17, lowering $T_c$ from 283 K (harmonic) to 260 K. The same framework reproduces the measured $T_c$ of YH9 to within about 3%, while underpredicting YH6 by about 26 K; a separate estimate based on cerium substitution in (Y,Ce)H10 gives 262 K as a consistency check. Experimentally, the paper contributes new transport and contactless radio-frequency data on YH6 and YH9, including narrow transitions approaching the thermal-fluctuation limit, a linear $dB_{c2}/dT = -0.52$ T/K slope, dirty-limit upper-critical-field behavior, and strong suppression of high-temperature superconductivity when palladium or aluminum is incorporated.
-
On the paper's own terms, the discovery is that a flat band with occupation $0<n(p)<1$ carries a nonzero anomalous density $\kappa(p)=\sqrt{n(p)(1-n(p))}$ even before any pairing interaction is turned on. Because the BCS gap equation then has a nontrivial solution proportional to $\lambda_0$ rather than exponential in $1/\lambda_0$, repulsive interactions ($\lambda_0>0$) can still produce a superconducting gap; the coupling constant acts only as a proportionality factor, not as the source of pairing. The same equations show that the superconducting gap deforms the flat band, converting the infinite effective mass into $M^*\propto 1/\Delta_1$, so the superfluid weight $D_s\simeq n_e e^2/M^*$ stays finite and a supercurrent can flow. The paper reads this as resolving the apparent paradox that flat bands have both zero kinetic energy and observed superconductivity.
-
The paper's central claim is that the continuously doping-dependent power-law self-energy observed at the node of high-$T_c$ cuprates is not a quantum-critical signature but a hydrodynamic consequence of poorly screened, spatially nonlocal repulsions. Its central result, Eqn. 6, gives $\Gamma_{\mathrm{inel}}(k_F,\omega,T)\approx A_\gamma T^\gamma \Phi_\gamma(\omega/T)$ with $\gamma=2-1/\alpha$, obtained from the dynamically screened interaction $W(q,\omega)$ whose superdiffusive pole follows from the $1/r^\alpha$ interaction. The derivation uses a diffusive irreducible polarization in the RPA combination $W^{-1}=V^{-1}+\Pi_{\mathrm{irr}}$; for $\alpha<2$ the characteristic momentum at energy transfer $\Omega$ scales as $q_\Omega\sim(\Omega/D_\alpha)^{1/\alpha}$, making tangential scattering dominate and producing scale covariance. The paper identifies the optimal-doping marginal Fermi liquid with $\alpha\to 1^+$ ($\gamma\to 1^+$), and increasing doping with larger $\alpha$ and larger fitted $\gamma$, up to the diffusive value $\gamma=1.5$ for $\alpha>2$.
-
The authors claim that 45°-twisted FeSe/cuprate heterostructures form a nearly ideal CuFe2 Lieb lattice, and that this lattice hosts altermagnetism through two cooperating routes. The first uses checkerboard antiferromagnetic order on the Fe sites together with finite Cu–Fe interlayer hopping t0 to generate a d-wave spin splitting. The second uses the substrate to break the equivalence of the two Se atoms, making the next-nearest-neighbor Fe–Fe hoppings alternate (t ± δt), which alone splits the bands. DFT for FeSe/Bi2Sr2CuO6 confirms both routes, with splittings of 15 meV in the BiO2-cleaved structure and 25 meV when the CuO2 plane is exposed, and the splitting is carried mainly by the Fe d
-
The central discovery is that an onsite Hund's exchange J can generate an effective attractive pairing channel in a single-band Hubbard model, even though U_eff = U - J remains predominantly repulsive. The paper derives the binding energy E_b = -(1/4)J n + (1/4)U_eff n^2, where n is the fractional band occupancy; the negative linear term dominates for small fractional n while the positive quadratic term wins near integer filling. This produces a superconducting dome in doping, with optimal doping p_opt = J/(2U_eff) + p_min and maximum gap Δmax = J^2/(16U_eff). The order parameter mirrors the tight-binding dispersion with d-wave symmetry for cuprates (via t_x = -t_y) and s±-wave symmetry for
-
A mechanism similar to the standard phonon drag can give rise to anomalies in the thermopower of a metal, if the dragged collective mode is overdamped, with a damping coefficient that increases with lowering the temperature. This finding adds a piece to the puzzle of the strange-metal behavior observed in many different systems and supports the proposal that overdamped charge density fluctuations can be responsible for such a behavior in high-temperature superconducting cuprates.
-
The author maintains that the Spin-Fermion-Hubbard Model, in which the Cu++ electrons form a square lattice of localized spins while the doped holes move along the oxygen sub-lattices and undergo a Kondo-like magnetic interaction with the localized spins besides the Hubbard-like electric repulsion, has led to a successful theory for High-Tc superconductivity in hole-doped cuprates, in contrast to the alternative that forms Zhang-Rice singlets and yields the t-J model.
-
It is proved that near the critical point the infinite-dimensional effective action is diffeomorphic to a finite-dimensional catastrophe. Starting from the Ginzburg-Landau free energy functional, the Euler-Lagrange partial differential equation can be reduced to the cusp catastrophe model. The fermionic imaginary-time path integral is carried to the same cusp form by the Hubbard-Stratonovich transformation, Matsubara frequency expansion, and Grassmann algebra. The resulting framework is connected to adsorption potential theory to account for the catastrophic topological character of electron pairing in high-temperature superconductivity.
-
Resonant inelastic X-ray scattering on HgBa₂Ca₂Cu₃O₈₊δ shows that the charge response is dominated by dynamic charge density fluctuations extending up to several hundred meV. At the momentum of maximum CDF intensity the paramagnon energy displays pronounced softening. The data therefore indicate a strong interplay among charge, lattice and spin excitations, supporting a cooperative mechanism in which the dynamic charge fluctuations mediate the coupling between these degrees of freedom.
-
In Bi2267, high-resolution ARPES identifies multiple hole Fermi pockets that carry substantial electron pairing, manifested as energy gaps up to 42 meV even in lightly doped planes with p approximately 0.05; this pairing supports superconductivity at approximately 75 K while strong antiferromagnetic order and correlations remain present, showing that the two orders can coexist in a multi-pocket cuprate.
-
The pairing mechanism is identified as the emergent local attraction counterintuitively generated from the originally strong local repulsion U. The emergent attraction is interpreted from attraction from reduced repulsion, originating from the release of the fluctuating doubly-occupied sites characterized from the false vacuum in the Mott insulator to the double-occupation-free d-wave SC states upon carrier doping. This instantaneous attraction is in contrast with the conventional BCS SC mediated by bosonic glues.
-
Bipolar doping is achieved in (Sr,Eu)CuO2 and (Ca,Li)CuO2+δ infinite-layer films. ARPES reveals persistent antiferromagnetic band folding that coexists with superconductivity in both doping regimes. At hole doping ~0.07 set by the Luttinger volume, the folding emerges directly from the Fermi arcs of the film’s single Fermi surface, and the superconducting onset temperature exceeds 60 K.
-
At sufficiently high pump fluences, 1.6 eV photoexcitation drives Bi2Sr2CaCu2O8+δ into a photostationary long-lived excited state whose Fermi surface undergoes a Lifshitz transition from hole-like to electron-like topology; the band evolutions are analogous to those from chemical doping and arise from a cooperative photodoping process involving charge transfer, effective-correlation renormalization, and defect-assisted trapping.
-
Hole doping in the infinite-layer cuprate is realized in Sr1-xRbxCuO2 thin films by the synergistic effect of rubidium substitution and apical oxygen incorporation; resistivity and magnetic-field measurements then show superconducting transitions with an onset temperature of 100 K, while structural analysis confirms the infinite-layer phase.
-
Using near 18,000 highly-cited publications over the past seven decades, we construct a structured knowledge graph linking competing superconducting mechanisms, material families, evidential modalities, and citation relations. We find that LLM-extracted representations recover coherent and physically interpretable structures, including family-dependent mechanism profiles, evidence-specific correlations, and citation-mediated temporal evolution of scientific beliefs. Ablation studies on LLM further show that the global structure remains robust across prompting, decoding, and model variations.
-
In (La,Pr)3Ni2O7 thin films, ultra-low temperature STM/S reveals an energy-symmetric, flat-bottom U-shaped gap around the Fermi level with zero residual density of states. This gap, combined with its reduction under 14 T c-axis magnetic field and rapid filling to V-shaped with increasing temperature, matches the expected behavior of a superconducting gap, implying a nodeless gap function at ultra-low temperatures. Electrical transport on the same film shows zero resistance with Tc above 20 K, supporting the superconducting nature.
-
The critical current density is strongly enhanced after the irradiation with its maximum at a dose of 1×10^16/cm², where the self-field critical current density at 2 K is enhanced from 5.5 MA/cm² to 26 MA/cm². At 77 K, the self-field critical current density for all irradiated crystals is over 0.1 MA/cm². The power-law dependence of the critical current density on the magnetic field is observed after irradiation, with a large power-law exponent α close to 1. A monotonic magnetic field dependence of the normalized magnetic relaxation rate is observed, which could be attributed to the low irreversibility field caused by the large anisotropy in Hg1223 single crystals. Through the analysis of a)
-
Well-defined spin excitations at Q = (0, 0.5, 2.5) exhibit a ~5 meV gap and anisotropic dispersions with zone-boundary softening transverse to the stripe direction. The full dispersion, including pronounced bilayer-periodicity modulations, is captured by a bilayer Heisenberg Hamiltonian with strong interlayer antiferromagnetic exchange and competing in-plane couplings inside a stripe-type magnetic order. Absolute normalization of the spectra shows that the spin-wave bandwidth reaches only about 25% of cuprate values, but enhanced local dynamic susceptibility yields a total fluctuating moment of comparable size.
-
In bilayer nickelates, superconductivity occurs in SDW-free, oxygen-stoichiometric regions. Spectroscopy indicates that a ligand hole resides mainly at the inter-bilayer apical oxygen, forming a robust interlayer five-spin polaron state that serves as the ground state, while oxygen deficiency favors SDW order instead.
-
The coupling of electrons and valence-flexible state of oxygen ions forms a charge-regulated interfacial layer induced by the adsorption potential, and electrons are paired by sharing the optimized interfacial structure and exchanging the adsorption mode, generating strong attraction to form Cooper pairs. The effective interaction potential between electrons is exactly derived, as well as the electron-adsorption-mode coupling strength, in which the adsorption coupling constant is up to 43.4. D-wave symmetry comes from the anisotropy of interfacial adsorption forces, the pseudo-energy gap behavior is explained, the coherence length from the one-dimensional Ginzburg-Landau equation matches the
-
We introduce a randomized, symmetry-preserving cooling algorithm that requires no spectral information, using only local coupling operators to ancilla degrees of freedom with randomly sampled energy splittings to drive generic fermionic systems toward their low-energy manifold. Across all models, we observe universal cooling behavior: monotonic energy relaxation, concentration of spectral weight at low energies, and stabilization of correlated ground-state order.
-
Ambient-pressure superconductivity emerges in La3Ni2O7 when grown as ultra-thin films under compressive strain from suitable substrates, paralleling the high-pressure superconductivity seen in bulk Ruddlesden-Popper nickelates.
-
The finite-temperature phase diagram of the t-t' Hubbard model, obtained via thermal tensor network simulations, displays a d-wave superconducting phase on the electron-doped side but a regime of strong pair-density-wave fluctuations on the hole-doped side. The PDW state involves inter-arc pairing with net momentum near (0, π), distinct from zero-momentum dSC pairing, and these fluctuating states fill the lower portion of the pseudogap regime, possibly transitioning to charge density wave order upon cooling.
-
In the non-engineered SU(4) model, charge-4e superconductivity is the primary ground state at zero temperature in the strong-coupling regime. At finite temperature, in the absence of charge-2e superconductivity, a Berezinskii-Kosterlitz-Thouless transition occurs with a universal jump in superfluid stiffness matching a charge-4e condensate, and the transition temperature increases nearly linearly with interaction strength while a pseudogap opens from strong phase fluctuations.
-
The magnitude of the room-temperature “drop-effect” (weight loss of sealed reactors containing powdered LBCO or YBCO plus a crystal hydrate under a high-frequency field) depends on doping almost exactly as Tc(p) does, including a maximum near optimal doping and a clear suppression near p = 1/8.
-
Epitaxial compressive strain from substrates such as SrLaAlO4 enables ambient-pressure superconductivity with Tc exceeding 40 K in bilayer La3Ni2O7 thin films (and related Pr- or Sr-doped variants), converting the high-pressure bulk discovery into a practical thin-film platform whose electronic structure, Fermi-surface topology, and pairing symmetry can now be probed and tuned at ambient pressure.
-
The central discovery is a doping-controlled correlation: coherent, dispersive spin excitations—the signature of collinear double-stripe magnetic correlations with a dominant interlayer exchange SJz ≈ 44 meV—remain essentially unchanged in energy and damping across x=0 to 0.21, where the films superconduct, and collapse at x=0.38, where superconductivity is gone. The collapse is selective: the ~1.0 eV intra-atomic dd excitation is unchanged, but the ~0.4 eV bilayer eg-sector excitation (sensitive to apical-oxygen interlayer hopping) and the ~1.6 eV mixed dd/charge-transfer feature are strongly suppressed. The authors interpret this as a selective doping-induced orbital reconstruction that de
-
Starting from a microscopic fermionic theory, the Cooper-channel kernel admits a universal spectral representation in terms of the time-scale density of states (TDOS) of collective decay modes, without invoking a specific bosonic mediator. A finite TDOS at vanishing relaxation rate produces a memory-dominated regime characterized by long-time kernels K(t)∼1/t and logarithmic enhancement of the retarded pairing interaction, leading to a BCS-like exponential transition scale set by infrared spectral weight. More generally, infrared-singular spectra generate power-law response and algebraic enhancement of the transition scale. The same relaxation spectrum controls normal-state dynamics, giving
-
The paper's central claim is that the cuprate Tc–p dome is a composite of two extrinsic suppression mechanisms imposed on a simple intrinsic law. In a clean CuO2 plane, Tc should follow the Bose–Einstein condensation temperature of preformed pairs, rising linearly with the mobile hole concentration p; the pairing glue is the antiferromagnetic background, and the Cooper pair is a d-wave singlet formed either between hole-doped composite singlets (underdoped, BEC side) or between band-like d holes (overdoped, BCS side). The parabolic dome and the supposedly universal optimal doping p = 0.16 are artifacts of randomness: random block-layer charges trap holes at low doping and cause pair breaking
-
The central claim is that the newly observed splitting of the 45 meV mode together with the 60 meV feature in the doped compounds is consistent with an enhanced interlayer coupling SJ⊥ of roughly 69-73 meV within the stripe-type Heisenberg model, while the intralayer couplings remain weak; the Nd-doped sample exhibits stronger fluctuations than either the undoped or Pr-doped material.
-
The paper's central claim is that the indirect attraction between two h+-Cu-h+ Cooper pairs, mediated by the oxygen anion that sits between them (bridge-II), overcomes their direct Coulomb repulsion. At the superconducting transition, this net attraction makes the preformed pairs 'hold hands' across the CuO2 plane and undergo Bose-Einstein condensation. The quantitative content is Eq. (3): Tc = Tc0 (1 - 3.426 a/λ0), so Tc increases linearly as the pair-pair scattering length a becomes more negative. The same double-bridge logic is extended to electron pairs, to nickelates, and to other strongly ionic superconductors, making the proposal a universal route rather than a cuprate-specific fix.
-
The central claim is that the Josephson diode effect (JDE) in a planar s-d-s junction arises when asymmetric s-d couplings pin the stronger interface phase to φ2 = π/2, spontaneously breaking time-reversal symmetry, and when single-Cooper-pair tunneling is enabled at the weakly coupled interface. The resulting 1D potential, E(φ1) = E_J1^(2) cos2φ1 + E_J1^(1) cosφ1 ± E_Js^(1) sinφ1, contains coexisting cosφ1 and sinφ1 terms that break all Z2 symmetries and yield unequal forward and backward critical currents. The maximal diode efficiency approaches 1/3, and its polarity reverses across a critical angle θc; with zero s-wave admixture (Δds = 0), θc = π/4, while Δds > 0 shifts θc below π/4 and Δ
-
In optimally doped La-Bi2201, spatially resolved transient reflectivity measurements show that micrometer-scale contrasts arise from local variations in the threshold fluence to disrupt the superconducting or pseudogap state. The superconducting response is spatially uniform while the pseudogap is inhomogeneous, yet their threshold fluences closely track each other, providing direct spatial evidence of a robust local correlation between the two states.
-
In La4Ni3O10, ligand holes reside in the p_x,y orbitals of planar oxygen and the p_z orbitals of apical oxygen, hybridizing respectively with the Ni d_x2-y2 and d_z2 orbitals. This hybridization enables orbital-selective O K-edge RIXS, which demonstrates that d_x2-y2 states dominate low-energy charge excitations and are more itinerant than d_z2 states. The observation of a ~0.1 eV bimagnon in both RIXS and Raman spectroscopy indicates an interlayer superexchange interaction J_z of ~50 meV.
-
The central claim is that a 3D network of boron-doped, zeolite-confined (2,1) carbon nanotubes undergoes a transition into a phase-coherent superconducting condensate at ambient pressure near 230 K. Boron doping positions the Fermi level close to a van Hove singularity, enhancing the density of states; the zeolite's ~5 Å channels stabilize (2,1) tubes that are otherwise dynamically unstable. Four complementary probes—DC magnetization, specific heat, two-probe resistance, and point-contact spectroscopy (three gaps, leading gap ~30 meV, BTK fits, tunable between tunnelling and Andreev limits)—yield mutually consistent Tc values in the range 220–250 K, with a resistive onset near 278 K and an e
-
The paper's central claim is stated in the introduction: the layers in multilayer nickelates are strongly coupled, indicating that superconductivity arises collectively in the multilayers. This distinguishes them from multilayer cuprates, where superconductivity primarily resides within individual CuO2 planes that are only weakly coupled. The review uses this lens to organize the field, from the 3d9 infinite-layer LaNiO2 (Tc up to ~40 K) to the pressure-induced superconductivity of the bilayer La3Ni2O7 (onset ~80 K in bulk, ~48 K in thin films) and trilayer La4Ni3O10 (~30–40 K). Along the way it cites bulk diamagnetic shielding above 90% in pressurized La2PrNi2O7 as the strongest evidence th
-
The central claim is that all three generally recognized prerequisites for high-temperature superconductivity — a high density of states at the Fermi level, strong coupling of electrons to another degree of freedom, and tunability — are present in the surface Fermi arcs of t-PtBi2. On the decorated-honeycomb (DH) termination, the arc dispersion contains a type-I van Hove singularity whose logarithmic density of states is measured about 5–8 meV below the Fermi level. On the Kagome-type (KT) termination, the arc center shows a splitting into two branches with a nearly flat lower branch and a Fermi-velocity renormalization factor of about 2.5, attributed to strong momentum-dependent coupling to
-
The central claim is that the nanoscale geometry of lattice and charge heterogeneity is intrinsic, not incidental, to the mechanism that raises quantum coherence to high temperature in cuprate superconductors. On the paper's terms, the two-site Cu–O pair distributions detected by EXAFS and often attributed to static disorder are in fact a signature of dynamic charge–lattice tunneling, and the synchronization of these internal quantum tunneling polarons—described by a mapping of the cluster Hamiltonian onto the Kuramoto model—together with local Euclidean Q-ball condensates, constitutes the microscopic route to superconducting condensation. The authors assert that the same physics explains the pseudogap, the strange-metal linear resistivity, and the diamagnetism above $T_c$, and that artificially grown superlattices confirm the link by tuning $T_c$ through the nanoscale geometry. A sympathetic reader is asked to accept that high-temperature superconductivity is a property of an anharmonic, inhomogeneous lattice landscape rather than of a clean Fermi surface.
-
The paper's discovery is that a wedge-shaped stack of intrinsic Josephson junctions in BSCCO rectifies supercurrent without any twist or artificial barrier. The diode effect is controlled by the out-of-plane component of the magnetic field, not the in-plane component, and it disappears in the model when the current-phase relation is purely sinusoidal: only the anharmonicity $\kappa$, which is large because the junction barrier is one atomic layer thick, turns field-induced symmetry breaking into $I_{c+} \neq |I_{c-}|$. The paper establishes the junction-number rule $i = \sin[\frac{1}{N}(\phi - \frac{2e}{\hbar}\int \vec A \cdot d\vec l - \kappa i)]$, verifying experimentally that fewer juncti
-
The central discovery is a continuous, gate-tuned phase diagram in 4.6° twisted WSe2 that reproduces the essential phenomenology of doped Mott insulators. At $\nu=1$ the system is an antiferromagnetic insulator with a Néel temperature near 8 K, and both electron and hole doping turn it into a doped antiferromagnetic metal with a small Fermi surface. Adjacent to the Mott transition, superconductivity forms in domes on both sides, with the highest $T_c$ located near the boundary where antiferromagnetism disappears. At that boundary the Hall density jumps by roughly one moiré density, which the authors interpret as the collapse of the Mott gap and a reconstruction of the Fermi surface, analogous to the pseudogap critical point in cuprates. Away from the insulator, the normal state shows $T$-linear resistivity over the full temperature range with near-Planckian scattering, and on one side the $T$-linear region extends over a wide doping range rather than being confined to a single quantum critical point.
-
In (Cu,C)Ba2Ca3Cu4O11+δ, ARPES measurements show that the outer CuO2 planes are not superconducting at the material's Tc of 110 K. The inner underdoped CuO2 planes instead exhibit large pairing strength and phase coherence at a doping level of 0.07 holes per Cu. These observations establish that high Tc is primarily driven by the inner planes and that CuO2 planes free of apical oxygen can support superconductivity up to 110 K in the deep underdoped regime. The findings indicate that the composite picture of strong proximity effects between inner and outer planes is not universally required for high Tc in multilayer cuprates.
-
On its own terms, the paper's central claim is that Fm-3m-LaH10 — the hydrogen-rich lanthanum superhydride with a face-centered cubic structure that superconducts near 250 K — does not decompose on a timescale of months or years under the conditions used to synthesize it. The evidence is longitudinal: for one sample, X-ray diffraction one week and 55 months after synthesis shows the same Fm-3m phase with lattice parameters within 0.5%, and resistance at 34 months gives a superconducting transition near 247 K; for a second sample, resistance measurements 2 days, 8 months, and 66 months after synthesis all show a transition near 250 K, with X-ray diffraction about one month after synthesis confirming the Fm-3m phase. A sample decompressed to 120 GPa distorted structurally and lost its high Tc, but recompression to 136 GPa restored Tc around 241 K, showing that the phase is robust over a pressure range rather than being a transient product. The paper further argues that the earlier NMR-based decomposition study never structurally characterized its samples and that its resistance data show transitions well below the ~250 K signature of Fm-3m-LaH10, so the proposed decomposition scenario likely refers to a different material.
-
The central claim is that the phases observed in cuprates and related materials should be understood as intertwined orders: the charge-density wave, spin-density wave, nematic, and $d$-wave superconducting states are related by symmetry to a common “mother” state, the pair-density wave, a superconductor in which the pairing amplitude modulates with a period of a few lattice constants. In the proposed Landau–Ginzburg theory, the PDW is described by two complex order parameters $\Delta_{\pm Q}$; from them the charge order $\rho_{2Q}\sim\Delta_{-Q}^*\Delta_Q$ and a charge-$4e$ condensate $\Delta_{4e}\sim\Delta_Q\Delta_{-Q}$ follow as induced composite orders. The argument explains the anomalous dynamical layer decoupling in La$_{2-x}$Ba$_x$CuO$_4$ at $x=1/8$, predicts half-vortices carrying half the usual flux quantum ($hc/4e$), and shows that in two dimensions thermal melting of the PDW produces vestigial CDW, nematic, and charge-$4e$ phases without fine-tuning. The paper concludes that many of the observed phases in these materials may arise from a common origin and from the same microscopic physics.
-
The paper's central discovery is that electronic nematicity—the spontaneous breaking of in-plane fourfold (C4) rotational symmetry down to twofold (C2) symmetry—exists in an electron-doped cuprate superconductor, Sr$_{0.9}$La$_{0.1}$CuO$_2$, and that it pervades both the normal state and the state reached when superconductivity is extinguished by a magnetic field. Using angle-resolved resistivity measurements with a cross-shaped device that rotates the current direction continuously, the authors find that the longitudinal resistivity oscillates as $\overline{\rho} + \Delta\rho\cos[2(\phi-\alpha)]$ and the transverse resistivity as $\Delta\rho\sin[2(\phi-\alpha)]$, giving a nematic amplitude $N = \Delta\rho/\overline{\rho}$ of about 1.5% at 300 K and a director $\alpha$ that shifts with temperature and rotates abruptly near $T_c$. The nematic amplitude is not changed when the substrate is switched from tetragonal KTaO$_3$(001) (in-plane lattice orthorhombicity below 0.05%) to orthorhombic GdScO$_3$(110) (film orthorhombicity 0.38%), while the director is pinned by the orthorhombic strain; the authors take this near-independence of amplitude as proof that the nematicity is electronic in origin. When a magnetic field of up to 16 T suppresses superconductivity at low temperature, the normal-state nematic amplitude and director are recovered at all temperatures below $T_c$, so the zero-temperature ground state is nematic. The nematicity also grows as the effective doping is reduced from optimal to underdoped, closely paralleling the behavior previously reported in hole-doped LSCO.
-
The central claim is that in (Hg,Re)1223, the superconducting gap of the outer CuO2 plane is substantially larger than in optimally doped Bi2223, while the inner-plane gap is comparable: 'the superconducting gap for the OP was significantly larger than that of the Bi-based one' and 'the enhanced pairing energy in the OP is essential for the highest Tc at ambient pressure' (abstract). Quantitatively, the paper reports Delta0(OP) = 57 +/- 1 meV versus about 43 meV for Bi2223, and Delta0(IP) = 63 +/- 3 meV, comparable to Bi2223's roughly 60 meV.
-
The paper's central claim is that a 380 mm 'Magic Box' magnetostatic cavity can house a $^{3}$He spin filter with a field-gradient contribution to the longitudinal relaxation time of at least 421 h in ambient conditions, derived from a measured total relaxation time of 130 h and a wall relaxation time of 238 h at 0.9 bar; simulations predicted 615 h for the optimized geometry, and even with a 2.1 T high-temperature superconducting magnet at the sample position the field-gradient relaxation time remains 124 h. The second central claim concerns cell-wall chemistry: caesium deposited on a (111) single-crystal silicon wafer and baked at 150°C for one week does not sit as a simple metallic overlayer but interacts chemically with the wafer's silicon dioxide surface, as evidenced by X-ray reflectometry features that the simple slab model (silicon substrate, SiO$2$ layer, caesium layer) fits only poorly, with a $\chi^2$ of 157. The authors present this as the first step of a systematic study of how alkali-metal coatings form and evolve under heat treatment, with the eventual aim of controlling the wall relaxation term in the $^{3}$He polarization decay.
-
The paper reports the creation and public release of a collaborative database at https://sc.hi-scale.grisenergia.pt/app whose purpose is to consolidate the material data needed to engineer high-temperature superconducting (HTS) devices. Its central claim is that this is the largest publicly available collection of such data, going beyond superconductors themselves to include the structural, cryogenic, electrical, and magnetic materials an HTS device integrates. Every entry is meant to be traceable to a peer-reviewed source or validated manufacturer data, tagged with DOIs where possible, and structured through an ontology-driven JSON data model so the categories and properties can be extended without rebuilding the system. The authors position the database not as a static archive but as a peer-reviewed community resource whose contribution pipeline keeps it current.
-
We identify emergent spectral features on both occupied and unoccupied states that are consistent with excitations driven by quantum charge fluctuations. The results obtained in this study offer direct experimental insight into charge fluctuations in cuprates, thereby paving the way towards clarifying their fine electronic structure and the mechanism of high-Tc superconductivity.
-
On the paper's own terms, the discovery is an energy ordering established by unbiased variational optimization: in the two-orbital bilayer model with parameters from band-structure studies, the Jastrow-projected BCS ansatz with s±-wave pairing lowers the ground-state energy more than the analogous d_{$x^{2}$-$y^{2}$}-wave ansatz. For the Hubbard model, s± is favored for Hund's coupling above about 0.2 eV; for the extended t-J model, it wins over the entire parameter range studied. The optimized pairing amplitudes show the dominant component is $\Delta^z_{ij}$ on the vertical bond between 3d_{$3z^{2}$-$r^{2}$} orbitals, with onsite pairings of opposite sign on the two orbitals, consistent with pair-hopping. The result bridges the weak-to-moderate coupling regime, where renormalization-group studies find s±, and the strong-coupling regime, where the t-J model applies. A secondary finding is that intra-orbital double occupancy stays finite as U grows, so the electrons do not become well-defined local moments despite strong correlations.
-
The central claim is that the superconducting transition of Nb0.44Ti0.56 remains detectable through modulated ac susceptibility from 5 GPa to 160 GPa, with Tc rising from 9.6 K and then leveling off, matching the pressure dependence previously seen in resistance measurements. This establishes the alloy as a practical reference for the hydride debate, where resistance signatures of high-Tc superconductivity have not yet been matched by consistent diamagnetic evidence. The paper proposes that at any fixed pressure Pi, the ratio SI_sample(Pi)/SI_Nb0.44Ti0.56(Pi) separates bulk from non-bulk superconductivity: a ratio near 1 indicates bulk behavior, a ratio far from 1 indicates only a partial superconducting volume fraction. This is the first demonstration that such a reference can track its diamagnetic signal over a record-wide pressure range.
-
The paper claims that lithium-doped compressed molecular hydrogen adopts a cubic LiH12 phase in which the hydrogen sublattice remains molecular, with H-H bond lengths near 0.83 Å, distinctly shorter than the roughly 1.05 Å H-H separation of atomic hydrogen metal. Charge transfer of about 0.8 electron per Li to the H2 units tunes the interaction between bonding and antibonding 1s states, closing the insulating gap while preserving the molecules, and the Li ions stabilize the distorted H2 network ionically. For this phase, the fully anisotropic Migdal-Eliashberg equations give an electron-phonon coupling constant near 2.83 and a superconducting transition above 300 K at 250 GPa, with the result remaining above room temperature even for a Coulomb pseudopotential of 0.20. The paper therefore presents cubic LiH12 as the only binary hydride predicted to superconduct at temperatures exceeding room temperature.
-
The low-energy electronic phenomenology is dominated by oxygen-centered planar orbitals, which evolve from the d_3x2-r2 and d_3y2-r2 symmetry characteristic of 3-spin polarons to the familiar d_x2-y2 Zhang-Rice singlets that support high-temperature superconductivity in cuprates. By inclusion of magnetic moments on plaquettes of oxygen orbitals in the model, ZRS-like states mediate the SDW. Combined with the observation that oxygen annealing is required to induce superconductivity, this demonstrates that the ZRS population dictates whether the ground state favors density-wave order or superconductivity, with hole doping suppressing the former and stabilizing the latter.
-
The paper's central claim is that the temperature dependence of the BSCCO-induced NV relaxation rate $\Gamma_1(T)$ at zero field is a direct readout of three distinct low-energy dynamical regimes in a thin-film cuprate. At $T \ll T_c$, $\Gamma_1 \propto T^2$, consistent with nodal d-wave quasiparticles at BCS mean-field level. Near $T_c \approx 90$ K, $\Gamma_1$ rises in a sharp symmetric peak that scales as $|T-T_c|^{-x}$ with $x \approx 1$, clearly distinct from the BCS prediction $x = 1/2$; the paper attributes this extra singularity to amplitude and phase fluctuations of the superconducting order parameter. A TDGL Langevin equation with Gaussian white noise, treated with mean-field exponents $\nu = 1/2$, $z = 2$, reproduces the divergence on both the metallic and superconducting sides and yields fitted relaxation-time ratios $\tau^{\rm fit}_{\rm M}/\tau_{\rm GL} \approx 1.2$ and $\tau^{\rm fit}_{\rm SC}/\tau_{\rm GL} \approx 0.2$, bracketing the analytical weak-coupling values $1$ and $0.5$. In an applied field the transition peak broadens and becomes asymmetric as vortices enter, with $\Gamma_1 \propto H$ as expected for a diffusive vortex liquid; $T_2$ noise spectroscopy additionally resolves MHz-frequency fluctuations assigned to vortex motion in the vortex solid deep below $T_c$.
-
The authors claim that annealing as-grown La3Ni2O7 single crystals in ~10 MPa oxygen at 500 °C for about 12 hours produces a zero-field-cooled magnetization drop near 80 K, which they interpret as the Meissner effect of a superconducting transition at ambient pressure. The crystals show no zero resistance; instead, resistivity falls by about 30% between 80 and 20 K and then plateaus, consistent with small superconducting islands. The estimated superconducting volume fraction is at most 0.2%, and the signal is suppressed by fields up to 1 T without shifting the transition temperature. The authors attribute the effect to filamentary superconductivity, likely localized at boundaries of micrometer-scale domains of a nanoscale stripe phase, where residual strain mimics the effect of external pressure, and they propose that high-pressure oxygen annealing reduces oxygen vacancies, especially at the inner apical oxygen site, that otherwise suppress superconductivity.
-
On its own terms, the paper claims that the LSMO/YBCO heterostructure is "a unique case of overdoped YBCO keeping Cu-O chains and Cu-O planes intact." The core-level spectra of the bilayer shift uniformly by about 0.6 eV toward the Fermi level relative to bare YBCO, the spectral weight at the Fermi level is significantly enhanced, and a fit of the Cu 2p spectra with a cluster model gives a larger satellite-to-main intensity ratio and a larger density of delocalized ligand holes, which the authors interpret as an increase in the Cu 3d hole content of the Cu-O planes. That increase in hole concentration, without any change in oxygen content or lattice structure, is the overdoping claim. The paper also reports that the bilayer remains superconducting with $T_c \approx 86$ K, about 3 K lower than the bare YBCO film.
-
The paper's central claim is that in the range of parameters where high-temperature superconductivity arises, stripe ordering tendencies of some sort appear to be more or less ubiquitous. The supporting case is comparative: DMRG studies on Hubbard and t-J cylinders of width 2 to 8 find stripe or CDW-dominated ground states over broad parameter ranges, especially for t' ≤ 0; finite-temperature DQMC finds fluctuating stripe order in the normal state; and resonant X-ray and STM experiments report unidirectional CDW correlations in multiple cuprate families, strongest near x = 1/8 and always in competition with d-wave superconductivity. The authors argue these stripes arise from local phase separation in a doped Mott insulator rather than from Fermi-surface nesting. They also stress that weak X-ray intensities imply only small lattice displacements and hence do not measure the electronic condensation energy, leaving open whether the CDW is central or peripheral.
-
On the paper's own terms, the central discovery is that the cubic 216-type hydride Li2AuH6, isostructural to Mg2IrH6, is dynamically stable at ambient pressure, thermodynamically metastable (38 meV/atom above the 6LiH + 5Au reactant mixture, below the 80 meV/atom empirical threshold), and has superconducting transition temperature $T_c \approx 140$ K with electron-phonon coupling constant $\lambda = 2.84$ from anisotropic Eliashberg calculations. The Au-H octahedra provide a breathing $E_g$ mode at $\Gamma$ near 140 meV, but the largest contribution (about 70% of total $\lambda$) comes from low-frequency $A_{1g}$ and $E_g$ modes at the X point in which Li atoms vibrate together with H atoms. The authors conclude that strong electron-phonon coupling can arise without metallic covalent bonds, and they propose 'BCS superconducting units'—strongly coupled phonon modes—as the design target for high-$T_c$ conventional superconductors.
-
The central claim is that a bilayer two-orbital Hubbard model for La3Ni2O7, studied at the physical electron count N = 3, develops strong orbital-selective correlations because it sits close to a Mott transition at half filling N = 4. In this regime the z2 electrons are nearly localized and form interlayer spin singlets; the associated superexchange term, rewritten in the singlet channel and treated at saddle-point level, produces an additional splitting between the bonding and antibonding z2 bands. As a result the bonding–antibonding splitting remains sizable at about 1 eV even though the overall bandwidth is strongly renormalized. The paper states that this explains all four key features seen in ARPES and optical conductivity, and that the resulting picture provides the basis for a multiorbital t–J model of superconductivity in the bilayer nickelates.
-
On its own terms, the paper establishes that the mean valence of Ni ions in La$_3$Ni$_2$O$_7$ is pressure-independent, staying near 2.5+ from ambient pressure to 40 GPa at 20 K. The observed shift of the Ni K-edge white line is attributed to lattice contraction: the slope of energy shift versus Ni-O bond length is nearly the same for La$_3$Ni$_2$O$_7$, YNiO$_3$, and NiO, and density-functional calculations support this interpretation. The integrated white-line area changes slope at a critical pressure of about 12.5 GPa, signaling the orthorhombic-to-tetragonal structural transition that coincides with the disappearance of the DW and SDW orders and the onset of superconductivity. The natural reading of the data is that the structural phase transition plays the fundamental role in ceasing the competing orders and triggering superconductivity, while the mean valence of nickel stays constant.
-
The central claim is that epitaxial strain can replace hydrostatic pressure in the bilayer nickelate La3Ni2O7 family. The authors grow a 3-unit-cell La2.85Pr0.15Ni2O7 film by atomic-layer-by-layer epitaxy under strong ozone, post-anneal it in ozone, and find a resistivity onset at 45 K that coincides with the start of magnetic-field response. They interpret this as the onset of Cooper pairing in a two-dimensional superconductor. The zero-resistance state then develops through a BKT-like transition at TBKT = 9 K, and a mutual-inductance Meissner measurement gives TM = 8.5 K, matching TBKT. Structural probes show a single tetragonal phase coherently compressed by about 2 percent in the NiO2 planes, which the paper identifies as the key condition enabling the high onset without pressure.
-
On the paper's own terms, the central discovery is that the simple cubic (perovskite-like) hydride Pm-3m SrAuH3 is a conventional electron–phonon superconductor at zero pressure, with a critical temperature of 132 K computed from the Allen-Dynes modified McMillan equation (Coulomb pseudopotential $\mu^* = 0.13$). The phonon spectrum has no imaginary frequencies, the coupling constant is $\lambda = 2.025$ with logarithmic average phonon frequency $\omega_{\ln} = 806$ K, and the Eliashberg spectral function shows the coupling is carried mostly by acoustic and low-frequency optical vibrations below about 1200 cm⁻¹, with hydrogen modes higher up. Electronically, Au 5d orbitals dominate the density of states at the Fermi level and form a sharp van Hove singularity about 0.2 eV above $E_F$, which the authors credit for the strong coupling; the Fermi surface consists of a hole-like sphere at the zone center, cross-shaped sheets, and electron pockets at the zone corners. Stated generally, the paper claims that in this MXH3 family the X transition-metal atom, not hydrogen, controls the Fermi-level density of states and therefore the superconducting properties, and that seventeen of the 290 screened compounds are dynamically stable, with SrAuH3 and SrZnH3 exceeding 100 K at ambient pressure.
-
The paper's central claim is that a high-throughput workflow can uncover thermodynamically viable ternary clathrate hydrides whose superconducting critical temperatures reach or exceed room temperature, in structures too large for conventional structure-search methods. The headline result is type-III Na10Li5H86, a 202-atom cell whose electronic states at the Fermi level come almost entirely from hydrogen, with electron-phonon coupling $\lambda=3.61$ and log-averaged frequency $\omega_{\mathrm{log}}=948$ K, giving $T_c^{\mathrm E}=325$-$341$ K at 300 GPa with $\mu^*=0.10$-$0.13$. The same workflow reports near-room-temperature Eliashberg $T_c$ values for CaLi2H17 (326 K at 250 GPa), SrLi2H17 (309 K at 300 GPa), Na3ScH23 (289 K at 350 GPa), and BaLi5H34 (295 K at 300 GPa). The paper also claims that its modified AE model reproduces direct $T_c$ values with a mean absolute error of 24.5 K and that a cage-size match factor reliably predicts which hydrides will be at least metastable, providing a fast pre-screen for larger families of complex hydrides.
-
The central discovery is a predicted superconducting transition in the valence-electron fluid of two corrugated graphene sheets with intercalated CeH9 molecules. Using the lowest-order constrained variational method, the authors compute the free energy for 9900 distributions of CeH9 and find a second-order phase transition at Tc=198.61 K for the distribution n1=11, n2=6. Near the transition the magnetic susceptibility drops to approximately −1, the energy gap follows the superconducting gap relation, and the zero-temperature gap ratio is $2\Delta_0/(k_B T_c)=7.21$, roughly twice the BCS weak-coupling value; the authors classify this as unconventional, Hund's-metal-like superconductivity. They also estimate a critical current density of about $10^7$ A/cm2. The transition appears only when the electron effective mass is treated as a variational parameter that carries the electron-phonon coupling.
-
The central discovery is that the Ac-Be-H phase diagram contains a metastable fcc phase, AcBeH8, that remains dynamically stable from 200 GPa down to 10 GPa, with the electron-phonon coupling constant rising to $\lambda = 4.50$ and a predicted $T_c$ of 181 K at the lowest pressure. The paper reports other superconducting members of the same family: fcc AcBeH10 with $T_c \approx 165$ K at 300 GPa, AcBe2H16 with $T_c \approx 150$ K at 200 GPa, and thermodynamically stable phases with $T_c$ up to about 115 K at 200 GPa. It attributes the low-pressure behavior to BeH8 units embedded in the fcc actinium lattice: as pressure drops, soft phonon modes in the 110–540 cm$^{-1}$ range, dominated by hydrogen in those units, contribute about 60% of $\lambda$, and Fermi-surface nesting along W-L and X-W-K tracks the softening. The paper frames this as evidence that light-element M-H units can precompress hydrogen and stabilize high-$T_c$ hydride superconductivity close to ambient pressure.
-
The central claim is that $P\bar{3}m1$ AcBH7, a layered hexagonal phase in which each boron sits in a BH6 octahedron, remains dynamically stable at 70 GPa and has a superconducting critical temperature of 122 K, obtained by solving the Eliashberg equations with Coulomb pseudopotential $\mu^* = 0.10$. At 200 GPa the same phase has $T_c$ of only 43 K; decompression to 70 GPa softens four phonon modes, raises the electron-phonon coupling $\lambda$ from 0.67 to 1.98, and increases the hydrogen share of the Fermi-level DOS to 56%. The paper argues that the strong B-H interaction inside the BH6 units is what stabilizes the structure at submegabar pressure and drives the high $T_c$. It also compares with isostructural LaBH7, CeBH7, and ThBH7 to show that the H-dominated DOS at the Fermi level, not the total DOS, is the decisive factor for achieving high-temperature superconductivity.
-
Quenched disorder in these bulk crystals drives a quantum Griffiths singularity at the superconductor-metal transition, producing a divergent dynamical critical exponent that violates conventional scaling; the effect occurs for both perpendicular and parallel field orientations and persists to 5.3 K, allowing construction of a full quantum phase diagram for the three-dimensional anisotropic case.
-
Numerical simulations demonstrate that the superconducting critical temperature in the Su-Schrieffer-Heeger electron-phonon coupling model exceeds that of the Holstein model, particularly in the strong-coupling regime. This enhancement arises because SSH phonons not only induce strong electron pairing but also facilitate the phase coherence of Cooper pairs.
-
The central claim is that $Pb_{10-x}Cu_x(PO_4)_6O$, a modified lead apatite made by solid-state reaction, is a superconductor at room temperature and atmospheric pressure with $T_c$ above 400 K, and that its superconductivity is carried by a one-dimensional chain of $Cu^{2+}$ ions and bridging oxygens running along the c-axis. The evidence offered is bulk: a partially levitating pellet photographed and videoed at ambient conditions, zero-field-cooled and field-cooled magnetic susceptibilities whose room-temperature values exceed graphite's by factors the authors compute as roughly 5450 and 23, a four-probe resistivity that drops near $104.8^circ$C and stays at noise level over about 88 percent of $T_c$ in Kelvin, and current-voltage curves that show a jump between a gapped and an ungapped state which weakens with rising temperature and with applied magnetic field. The authors read the flat $dI/dV$ in the high-current region as evidence for s-wave pairing rather than a nodal gap, and they present a phase diagram linking the insulator-to-metal transition, the superconducting transition, and the metal-to-insulator reversal.
-
The central claim is that LK-99 is the first room-temperature, ambient-pressure superconductor, with a critical temperature above 400 K. The authors argue this from a set of standard superconducting signatures measured on bulk pellets and on a thermally evaporated thin film: voltage that stays at the noise floor as applied current is swept up and down, resistivity in the $10^{-10}$ to $10^{-11}$ $Ω·$cm range against the $10^{-11}$ $Ω·$cm criterion they cite from electrotechnical standards, diamagnetic field-cooled and zero-field-cooled magnetization under 10 Oe that stays negative to 400 K, and a critical current and critical field that do not vanish at the top of the measured range. They further argue that the superconductivity is intrinsic rather than induced by temperature or pressure, because the structure itself is already strained: Cu$^{2+}$ (87 pm) substitutes for Pb$^{2+}$ (133 pm) at the Pb(2) site of the phosphate network, shrinking the hexagonal cell from $a = 9.865$ Å, $c = 7.431$ Å to $a = 9.843$ Å, $c = 7.428$ Å, a 0.48 % volume reduction. Electron-density maps reconstructed from the (00$l$) and ($h$00) reflections show the Pb(1) ions of the cylindrical column displaced inward or outward, with the in-layer Pb(1)-Pb(1) spacing splitting from 3.03340 Å into 2.61815 Å and 5.23476 Å while the interlayer spacing stays near 3.7140 Å. The authors identify the resulting Pb(1)-phosphate interfaces as the superconducting layer.
-
The paper reports that the optical conductivity of La3Ni2O7 at low frequency cannot be fit with a single Drude term; it requires two, with distinct temperature behaviours. The first, D1, has a scattering rate following $1/ au_{D1} propto T^2$ over a broad range, the signature of a Fermi liquid. The second, D2, follows $1/ au_{D2} propto T$, the signature of a non-Fermi liquid. Cooling through $T^{ast} simeq 115$ K abruptly suppresses the D2 weight $omega_{p,D2}^2$ until it vanishes, transfers spectral weight from below roughly 600 cm$^{-1}$ up to about 6500 cm$^{-1}$, and leaves $omega_{p,D1}^2$ essentially unchanged. The authors extract a gap scale from the difference conductivity, $2Delta = 100.5$ meV, i.e. $2Delta/k_BT^{ast} = 10.14$, far above the weak-coupling BCS value of 3.52, and note that the gap's temperature dependence departs from BCS mean field near $T^{ast}$. Combined with their band-structure calculation, in which a flat hole-like Ni-$d_{3z^{2}-r^{2}}$ band and broad electron-like Ni-$d_{x^{2}-y^{2}}$ bands both cross the Fermi level, they conclude that the transition removes the Fermi-surface sheet dominated by the Ni-$d_{3z^{2}-r^{2}}$ orbital.
-
A suspended niobium sheet perforated with a periodic array of through-holes, originally fabricated to engineer its phonon spectrum, is reported to lose its electrical resistance at 175 K on cooling and to remain resistance-free up to 290 K on warming. The author argues that during processing the holey niobium has partially oxidized into a niobium–oxygen square lattice geometrically analogous to the copper–oxygen plane of cuprate superconductors, and that this Nb–O plane is the actual superconducting subsystem. Beyond zero resistance, the sample is reported to show a magnetization drop on cooling (Meissner effect) and a remnant magnetization at 300 K, which the author takes as together satisf
-
The paper's load-bearing assertion is that La3Ni2O7 hosts an s±-wave pairing instability with sign-reversing gaps on different Fermi surfaces, and that the Ni dz2 orbital together with its interlayer and intralayer exchange couplings is crucial for the high Tc. Concretely: 'An s±-wave pairing with sign-reversal gaps on different Fermi surfaces is revealed' (abstract:s5) and 'The Ni-dz2 orbital and its associated interlayer and intralayer exchange couplings are found to be crucial for the high-Tc superconductivity' (abstract:s6). If correct, the pairing symmetry of the 80 K nickelate is settled at the level of a strong theoretical prior, and the design lever for raising Tc is the dz2 bandwidth and hybridization rather than a copper-like d9 count.
-
The paper's core claim is that the essential low-energy physics of a CuO2 plane is captured by a charge triplet: each CuO4 plaquette lives in one of three effective valence centers, nominally Cu1+, Cu2+, or Cu3+, with distinct spin and orbital symmetry. These centers are mapped onto the three projections of an S=1 pseudospin, and the effective spin-pseudospin Hamiltonian includes on-site and inter-site density interactions, one-particle and two-particle transfer, and Heisenberg exchange. In the effective-field approximation with two sublattices and nearest-neighbor couplings, the model produces several Neel-like phases with a single nonzero local order parameter: antiferromagnetic insulator (AFMI), charge order (CO), glueless d-wave Bose superfluid (BS), and a metallic phase (FL). When Maxwell construction for first-order transitions is applied, phase-separated states emerge below a line T*(p), which the authors associate with the onset of the pseudogap phenomenon. With a suitable choice of model parameters, the resulting T-n phase diagram reproduces principal features of the experimental cuprate phase diagram.
-
The paper's central claim is that the inner (IP) and outer (OP) CuO2 planes of Bi2223 behave as two electronically independent layers with different doping, yet are coupled enough to share one bulk $T_c$ and one common relation between pair-breaking energy and doping. The two $B_{1g}$ Raman pair-breaking peaks—roughly 560 and 800 cm$^{-1}$ in the optimally doped crystal—are assigned to the OP and IP, respectively; an ARPES-based Kubo-formula calculation reproduces both peaks, confirming this assignment. Across four doping levels, all $B_{1g}$ peak energies collapse onto a single PE($p$) line once each plane's doping is estimated, meaning the double peak is simply the consequence of $p(\mathrm{OP})-p(\mathrm{IP})=0.076$. The authors emphasize that the important finding is the large normalized gap ratio PE/$k_BT_{c,\max}$ ($\sim$7–11 for $B_{1g}$), which is a common property of triple-layer cuprates; they attribute it to the underdoped IP, whose pseudogap enhances the antinodal pairing energy but, through proximity coupling, suppresses the bulk $T_c$ below what the pairing energy alone would allow.
-
The paper's central claim is that a pressure of 1.9 GPa does not suppress charge-density-wave order in YBa2Cu3Oy. The NMR quadrupole broadening that tracks the short-range CDW amplitude is essentially unchanged at both hole dopings measured (p0=0.109 and 0.125), and the quadrupole splitting that marks the high-field long-range CDW shows no more than a possible ten-percent change in amplitude while its onset field rises from about 9.9 T to 16.8 T (3.6 T/GPa), following the pressure-induced increase of the upper critical field. This directly contradicts x-ray studies reporting complete CDW disappearance by about 1 GPa. The paper argues that the contradiction can be resolved by recognizing an induced doping effect: pressure both intrinsically weakens CDW order and slightly increases hole doping, which masks the weakening near p0=0.109. With these two effects separated, the data are consistent with CDW order vanishing on a pressure scale of roughly 10-20 GPa—matching the scale on which Tc saturates near 107 K—so that most of the Tc enhancement under pressure may result from the weakening of CDW competition.
-
The paper's central claim is that the pseudogap critical point in a cuprate superconductor has a nematic character: as the hole doping approaches $p_c \approx 0.22$, the electronic nematic susceptibility $\chi_{\rm nem}$ diverges toward zero temperature, signalling a quantum critical point of an order that breaks the fourfold rotational symmetry of the CuO$_2$ plane. This is established by elastoresistance measurements, in which the strain-induced change of resistivity defines $\chi_{\rm nem} = d\eta/d\epsilon$ with the nematic order parameter $\eta = \Delta\rho/\rho$. Above $T^*$, $-\chi_{\rm nem}$ follows $\chi_{\rm nem} = \chi_0 + \lambda/[a(T-T_0)]$; the fitted Weiss temperature $T_0$ changes sign at $p \sim 0.2$ and, combined with a kink in $-\chi_{\rm nem}(T)$ at $T_{\rm nem} \approx T^*$ in underdoped and optimally doped samples, this locates the nematic instability at the pseudogap onset. The divergence of the susceptibility just below optimal doping, with $T_c$ still as high as about 70 K, implies that quantum critical nematic fluctuations coexist with high-temperature superconductivity and may contribute to pairing and to strange-metal transport.
-
The central claim is that Little-Parks oscillations in high-temperature superconductors, computed from a translation-invariant bipolaron Bose gas, are controlled by the phonon frequency $\omega$ through the polylogarithm $\mathrm{Li}_{1/2}(e^{-\alpha})$ with $\alpha = \omega/T_c$. In the soft-mode limit $\alpha \ll 1$ this term behaves as $\sqrt{\pi/\alpha}$, turning the oscillation amplitude into $\Delta T_c/T_c \approx 10^{-4}(T_c/\omega)^{1/2}$. Because this exceeds the BCS-based estimate when $\omega \ll T_c$, the author concludes that anomalously large critical-temperature oscillations are a signature of soft phonon modes and that the Little-Parks effect can be used to detect such modes in high-temperature superconductor nanostructures and to enhance $T_c$.
-
The paper's central claim is that the development of low-energy antiferromagnetic Cu-spin correlation in Pr$_{1-x}$LaCe$_x$CuO$_4$ is doping-dependent in the overdoped regime: it is present where superconductivity appears ($x = 0.14$, $T_c \simeq 20$ K, and $x = 0.17$, $T_c \simeq 5$ K), weakens with increasing $x$, and is negligibly small at $x = 0.20$, where the Meissner signal is unobservable. The evidence comes from zero-field and longitudinal-field muon spin relaxation spectra fitted with a two-component function that separates a stretched-exponential contribution (nuclear and Cu-spin fields) from a Gaussian contribution (static Pr$^{3+}$ moments). The absence at $x = 0.17$ and $0.20$ of a low-temperature steep increase in the relaxation rate $\lambda$ and of a recovery of the asymmetry toward 1/3 is read as the absence of appreciable Cu-spin correlation development. Combined with earlier results in the undoped and underdoped regimes, the authors conclude that low-energy Cu-spin correlation is intimately related to superconductivity in the entire doping range of the electron-doped cuprates.
-
The central claim is that experimental signatures reported in the referenced PNAS paper constitute evidence for vestigial nematic order that originates from local symmetry breaking in the cuprate pseudogap phase.
-
Superconductivity of high temperature cuprates is induced by the strong on-site Coulomb interaction, that is, the origin of high-temperature superconductivity is the strong electron correlation. Results on the ground state of electronic models for high temperature cuprates on the basis of the optimization variational Monte Carlo method show that a high-temperature superconducting phase will exist in the strongly correlated region.
-
The phenomenon of superconductivity occurs in the phase space of three principal parameters: temperature T, magnetic field B, and current density Jd. A seldom-measured parameter, the depairing current density Jd, holds the same fundamental importance as Tc and Bc2, in that it defines a boundary between the superconducting and normal states. A study of Jd sheds unique light on other important characteristics of the superconducting state such as the superfluid density and the nature of the normal state below Tc.
-
Using a local real-space microscopy probe, evidence is found of nanoscale interlayer defects along the c-crystallographic direction in BaFe2As2 based iron-arsenide superconductors. Ordered 122 atomic arrangements exist within the ab-plane and within regions of ~10 to 20 nm size perpendicular to this plane. While the FeAs substructure is very rigid, Ba ions are relatively weakly bound and can be displaced from the 122, forming stacking faults resulting in the physical separation of the 122 between adjacent ordered domains. The Cooper pairs may be finding a way around such localized interlayer defects through a percolative path of the ordered layered 122 lattice that may not affect Tc.
-
Helium ion beam irradiation of YBa2Cu3O7 produces Josephson junctions whose transport properties vary systematically with dose, crossing from SNS to SIS behavior, while series arrays of twenty such junctions exhibit identical critical currents and resistances with no appreciable device-to-device variation.
-
The paper's central claim is that the CEPC tunnel geometry can host a proton collider with about five times the LHC's collision energy and a peak luminosity well above it, and that this is worth aiming at because it opens the $O(10 text{ TeV})$ regime where naturalness, dark matter and the electroweak phase transition can be probed directly. Reaching 70.6 TeV in a 54.4 km ring requires 20 T dipoles, which the authors propose to build as two-in-one common-coil magnets combining Nb$_3$Sn outer coils with Bi-2212 high-temperature superconducting inner coils, giving a 22 T short-sample field at 4.2 K and a 50 mm aperture. The luminosity of $1.2times10^{35}$ cm$^{-2}$s$^{-1}$ follows from 5798 bunches at 25 ns spacing with $2times10^{11}$ protons each, $beta^* = 0.75$ m and a 73 $mu$rad crossing angle. The paper then works through the consequences: strong synchrotron damping at 35.3 TeV shrinks emittances on roughly one-hour timescales, so stochastic heating and luminosity leveling become required systems, and stored beam energy of 6.6 GJ per beam demands a five-stage collimation system roughly sixteen times more efficient than the LHC's.
-
The paper’s central claim is that phase transitions into the superconducting state in these materials occur by Bose-Einstein condensation of preformed electron pairs, not by the BCS mechanism. In this picture, the small O2− radius makes the metal sublattice a dilute gas of neutral atoms whose electron pairs (binding energy $\Delta_0$, e.g. 5.2 eV for Ba and 10.1 eV for Hg) are weakened by the dielectric medium to $\Delta_c = \Delta_0/\varepsilon^*$, and superconductivity sets in when the pair density is high enough that the BEC temperature $T_c \approx \Delta_c/(5.5 k_B)$ matches the data. The paper applies this to YBa2Cu3O7 (Tc≈90 K, $T_c^{\max}\approx 495$ K), YBa2Cu3Se7 (371 K), Ag2(Ag3Pb2H2O6) (~400 K), SrNbxTi(1−x)O3 (~0.3 K), and estimates active pair densities around $10^{20}$–$10^{21}$ cm$^{-3}$ and effective masses of several to more than a thousand electron masses. It also claims that once the system metallizes, $\varepsilon^*$ drops abruptly, the preformed pairs transmute into Cooper pairs, and BCS behavior with depairing takes over, so the BEC ceiling is the metallization temperature.
-
On the paper's own terms, the discovery is that ARPES reveals a universal kink in the nodal dispersion around 50-70 meV in all hole-doped cuprates, whose energy scale, temperature dependence, and isotope response point to coupling to phonons rather than to the magnetic resonance mode; and a second kink near the antinode whose energy shifts from roughly 40 meV in the normal state to roughly 70 meV in the superconducting state, consistent with the same B1g buckling phonon acting together with the d-wave gap. The authors further contend that underdoped spectra are polaronic, with a nearly vanishing quasiparticle weight that grows with doping, so that cuprates cross from a small-polaron regime to a Migdal-Eliashberg regime. Their concluding, forward-looking claim is that strong anisotropic electron-phonon coupling, particular phonon modes, and electron-electron vertex corrections may together yield an understanding of high Tc with d-wave pairing.
-
On the authors' own terms, the central discovery is that the pre-edge x-ray absorption spectrum of SCCO is not two peaks but four oxygen-site components: chain oxygens O(ch), ladder leg oxygens O(l)$_c$ and O(l)$_a$, and ladder rung oxygens O(r), whose distinct energies and polarizations permit a simultaneous fit to the $E\parallel c$ and $E\parallel a$ spectra. Using $$\delta_L = \frac{3(SW_{O(r)a}+SW_{O(l)a}+SW_{O(l)c})}{7(SW_{O(r)a}+SW_{O(l)a}+SW_{O(l)c}+SW_{O(ch)})},$$ they extract $\delta_L = 2.8/14$, $3.4/14$, and $4.4/14$ for $x=0$, $4$, and $11$, with chain densities $\delta_c = 3.2/10$, $2.6/10$, and $1.6/10$. These ladder densities sit very close to the $1/5$, $1/4$, and $1/3$ values required for hole crystals with periods $5c_L$, $4c_L$, and $3c_L$ when holes are paired on rungs, and the only one of these crystals not observed is the $4c_L$ state. Exact diagonalization of a minimal Heisenberg ladder with a cyclic four-spin exchange term shows an even-odd oscillation in the ground-state energy per rung that makes a disordered mix of two-rung and four-rung plaquettes cheaper than the ordered $4c_L$ state, explaining its absence. The paper concludes that this constitutes strong support for rung-based hole pairing in the ladders.
-
The central claim is that pairing is not exclusively in the CuO2 layers. In the highest-Tc cuprates, the charge reservoir layers containing Tl, Bi, or Hg contribute additional pairing through negative-U centers: at those sites the effective on-site interaction between two electrons is attractive because electronic or lattice polarization overcomes the Coulomb repulsion. Coherence between these centers and the CuO2 planes suppresses phase fluctuations and raises Tc, explaining why inserting such a reservoir layer can more than double the transition temperature of an otherwise comparable 214-type cuprate. For the chain-layer cuprates, the paper cites NQR relaxation in Pr-247 as direct evidence that superconductivity originates in the double zigzag Cu-O chains, and it proposes a linear, spin-zero, charge-one quasiparticle formed by binding a doped hole to a charge-transfer exciton (the eh particle) as the carrier of pairing in both chains and planes.