STM spectroscopy on bilayer nickelate ultrathin films reveals reproducible U-shaped spectra with nodeless gaps of ~14 and ~20 meV and flat zero-conductance regions.
Electronic structures across superconductor-insulator transition in Ruddlesden-Popper bilayer nickelate films
9 Pith papers cite this work. Polarity classification is still indexing.
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abstract
High-transition-temperature ($T_{C}$) superconductivity is recently discovered in Ruddlesden-Popper (RP) nickelate films with extraordinarily strong oxidation. While investigating phase diagrams is essential for uncovering the superconducting mechanism, the oxygen-tuned superconductor-insulator transition (SIT) in RP nickelates differs fundamentally from that in cuprates or iron-based systems. Here, we unveil the evolution of electronic structure in RP bilayer nickelate thin films across the SIT, combining angle-resolved photoemission spectroscopy (ARPES) and X-ray absorption spectroscopy (XAS) for both occupied and unoccupied states. In the superconducting state, a coherent quasiparticle band near Fermi level ($E_{F}$) coexists with an incoherent waterfall feature at high energy, paralleling that in cuprates. Approaching the insulating state with oxygen deficiency, the spectral weight of the occupied coherent quasiparticle band is gradually suppressed, accompanied by pronounced density of states redistribution and orbital reconfiguration in unoccupied states. These results reveal the electronic origin of the SIT in the phase diagram, which transcends carrier doping effects and oxygen vacancy states. Our findings point to a decisive role of oxygen in shaping the essential electronic landscape of RP bilayer nickelates, offering crucial insights into the superconducting mechanism.
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UNVERDICTED 9representative citing papers
Compressive strain and oxygenation in (La,Pr)₃Ni₂O₇₋δ films delocalize Ni 3d_z² and O 2p_z orbitals, suppress long-range spin-density-wave order, and preserve short-range magnons as prerequisites for superconductivity.
ARPES on (La,Pr,Sm)3Ni2O7 films reveals quasi-2D dx2-y2 bands, finite kz dispersion on dz2 bands, and a superconducting gap of ~18 meV with 2Δ/kBTc ~8 on the dz2-derived band.
Varying the Ni-Ni interlayer distance switches La3Ni2O7/LaAlO3 films between C-type and G-type spin density waves, with s± superconductivity emerging in between.
Terahertz spectroscopy on (La,Pr)3Ni2O7 films indicates disordered s±-wave pairing in the superconducting state and a distinct normal-state pseudogap above Tc onset.
Resonant x-ray scattering on La2PrNi2O7 films reveals superconductivity in SDW-free oxygen-stoichiometric regions with distinct c-axis electronic structure, proposing an interlayer five-spin polaron ground state.
DFT-based tight-binding models and FRG calculations predict that reducing in-plane lattice constant or increasing out-of-plane constant in La3Ni2O7 films increases Fermi-level DOS and enhances Tc while preserving s± pairing.
Compressive strain enhances Jahn-Teller splitting Δ_JT in La3Ni2O7 films as the key microscopic tuning parameter for superconductivity, matching ARPES and Hall data on specific substrates.
The review covers experimental and theoretical progress on superconductivity in Ruddlesden-Popper nickelates, emphasizing ambient-pressure thin-film results in La3Ni2O7.
citing papers explorer
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Atomically resolved intrinsic superconducting gap in (La,Pr)3Ni2O7 films
STM spectroscopy on bilayer nickelate ultrathin films reveals reproducible U-shaped spectra with nodeless gaps of ~14 and ~20 meV and flat zero-conductance regions.
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$3d_{z^2}$ orbital delocalization and magnetic collapse in superconducting (La,Pr)$_3$Ni$_2$O$_{7-\delta}$ films
Compressive strain and oxygenation in (La,Pr)₃Ni₂O₇₋δ films delocalize Ni 3d_z² and O 2p_z orbitals, suppress long-range spin-density-wave order, and preserve short-range magnons as prerequisites for superconductivity.
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Three-Dimensional Electronic Structures in Superconducting Ruddlesden-Popper Bilayer Nickelate Films
ARPES on (La,Pr,Sm)3Ni2O7 films reveals quasi-2D dx2-y2 bands, finite kz dispersion on dz2 bands, and a superconducting gap of ~18 meV with 2Δ/kBTc ~8 on the dz2-derived band.
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Tunable superconductivity and spin density wave in La3Ni2O7/LaAlO3 thin films
Varying the Ni-Ni interlayer distance switches La3Ni2O7/LaAlO3 films between C-type and G-type spin density waves, with s± superconductivity emerging in between.
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Multimodal Terahertz Spectroscopy of the Pairing Symmetry and Normal-State Pseudogap in (La,Pr)$_3$Ni$_2$O$_7$ Films
Terahertz spectroscopy on (La,Pr)3Ni2O7 films indicates disordered s±-wave pairing in the superconducting state and a distinct normal-state pseudogap above Tc onset.
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Interlayer Five-Spin Polaron in Superconducting Bilayer Nickelates
Resonant x-ray scattering on La2PrNi2O7 films reveals superconductivity in SDW-free oxygen-stoichiometric regions with distinct c-axis electronic structure, proposing an interlayer five-spin polaron ground state.
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Jahn-Teller distortion on strained La$_3$Ni$_2$O$_7$ thin films
Compressive strain enhances Jahn-Teller splitting Δ_JT in La3Ni2O7 films as the key microscopic tuning parameter for superconductivity, matching ARPES and Hall data on specific substrates.
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Superconductivity in Ruddlesden-Popper nickelates: a review of recent progress, focusing on thin films
The review covers experimental and theoretical progress on superconductivity in Ruddlesden-Popper nickelates, emphasizing ambient-pressure thin-film results in La3Ni2O7.