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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Superconducting gap structure and bosonic mode in La2PrNi2O7 thin films at ambient pressure
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abstract
The recent discovery of high temperature superconductivity in nickelate systems has generated tremendous interests in the field of superconductivity. The core issue to understand the superconductivity mechanism is about the superconducting gap and its symmetry. By using the substrate of SrLaAlO4(00l), we have successfully synthesized the superconducting thin film of La2PrNi2O7 with Tc(onset) = 41.5 K. Superconducting tunneling spectra are successfully measured on the terraces after we expose the superconducting layer by using the tip-excavation technique. The spectrum shows a two-gap structure with Delta1=19 meV, Delta2=6-8 meV, and fittings based on the Dynes model indicate that the dominant gap should have an anisotropic s-wave structure, this allows us to put the priority in selecting the s+- among the two arguable pairing models: s+- and d-wave. Furthermore, a clear bosonic mode with energy Omega=30+-2 meV is observed, which further supports a sign reversal gap. Our results shed new light in understanding the mystery of superconductivity in bilayer nickelate superconductors.
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Observation of an energy-symmetric flat-bottom U-shaped gap with zero residual DOS in (La,Pr)3Ni2O7 thin films, showing unconventional temperature evolution and magnetic field suppression consistent with a nodeless superconducting gap.
Single-crystal neutron scattering establishes stripe antiferromagnetic order with strong interlayer coupling and competing in-plane exchanges in La3Ni2O7, yielding fluctuating moments comparable to cuprates but with lower bandwidth.
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.
s±-wave pairing in La3Ni2O7 thin films is robust across different crystal structures, and the halved transition temperature is reproduced only when the experimentally determined structure with small interlayer hopping is used.
A two-component scenario unifies key observations in bilayer nickelate superconductivity, predicting doping-dependent superconducting domes and normal-state behaviors that differ by interlayer coupling strength.
The superconducting T_c of La3Ni2O7 is controlled by the d_x2-y2 orbital filling and the interlayer magnetic exchange J_perp, so clean electron doping should raise T_c.
Constrained-path QMC simulations of a bilayer Hubbard model map a crossover from d-wave to s±-wave pairing driven by Hund's coupling and crystal field splitting in La3Ni2O7.
La3Ni2O7 exhibits s±-wave two-gap superconductivity with out-of-plane Ni-dz2 pairing dominant under pressure and in-plane Ni-dx2-y2 pairing in thin films, with the Tc drop attributed to reduced inter-layer hopping.
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.
Epitaxial strain enables ambient-pressure superconductivity in bilayer nickelate films, facilitating detailed studies of their properties and phase diagrams.
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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Observation of flat-bottom U-shaped energy gap in high-Tc nickelate (La,Pr)3Ni2O7 thin films
Observation of an energy-symmetric flat-bottom U-shaped gap with zero residual DOS in (La,Pr)3Ni2O7 thin films, showing unconventional temperature evolution and magnetic field suppression consistent with a nodeless superconducting gap.
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Nature of magnetism in bilayer nickelate La3Ni2O7 single crystals
Single-crystal neutron scattering establishes stripe antiferromagnetic order with strong interlayer coupling and competing in-plane exchanges in La3Ni2O7, yielding fluctuating moments comparable to cuprates but with lower bandwidth.
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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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Theoretical study on ambient pressure superconductivity in La$_3$Ni$_2$O$_7$ thin films : structural analysis, model construction, and robustness of $s\pm$-wave pairing
s±-wave pairing in La3Ni2O7 thin films is robust across different crystal structures, and the halved transition temperature is reproduced only when the experimentally determined structure with small interlayer hopping is used.
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A unified theory of thin film and bulk bilayer nickelates
A two-component scenario unifies key observations in bilayer nickelate superconductivity, predicting doping-dependent superconducting domes and normal-state behaviors that differ by interlayer coupling strength.
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Filling and Interlayer Superexchange Control Superconductivity in La$_3$Ni$_2$O$_7$
The superconducting T_c of La3Ni2O7 is controlled by the d_x2-y2 orbital filling and the interlayer magnetic exchange J_perp, so clean electron doping should raise T_c.
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Pairing Symmetry Crossover from $d$-wave to $s_{\pm}$-wave in a Bilayer Nickelate Driven by Hund's Coupling and Crystal Field Splitting
Constrained-path QMC simulations of a bilayer Hubbard model map a crossover from d-wave to s±-wave pairing driven by Hund's coupling and crystal field splitting in La3Ni2O7.
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Unconventional Superconductivity in $\mathrm{La_{3}Ni_{2}O_{7}}$ from the Perspective of Symmetry
La3Ni2O7 exhibits s±-wave two-gap superconductivity with out-of-plane Ni-dz2 pairing dominant under pressure and in-plane Ni-dx2-y2 pairing in thin films, with the Tc drop attributed to reduced inter-layer hopping.
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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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Experimental Progress in Ambient-Pressure Superconducting Bilayer Nickelate Films
Epitaxial strain enables ambient-pressure superconductivity in bilayer nickelate films, facilitating detailed studies of their properties and phase diagrams.
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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.
- Orbital-Selective Diagonal-Gap Test of Pairing in La$_3$Ni$_2$O$_7$
- Electron Doping of $\mathrm{La_3Ni_2O_7}$ Thin Films: Candidate Metal Dopants and Their Potential Impact on Superconductivity