Two-gap superconductivity and decisive role of rare-earth d electrons in infinite-layer nickelates

ORAL

Abstract

In 2019, superconductivity was discovered in infinite-layer nickelates, which has a latest experimental Tc up to 23 K. The conventional mechanism for superconductivity – phonon-mediated pairing – was presumably ruled out because density functional theory (DFT) calculations reported a very weak electron-phonon (e-ph) coupling. Here, by performing ab initio GW calculations for the electronic structure and the e-ph coupling, we discover that infinite-layer Nd0.8Sr0.2NiO2 is a dominantly two-gap phonon-mediated superconductor. We show electron correlations (self-energy effects going beyond DFT) alter dramatically the orbital character of its multi-band Fermi surface and also strongly enhance the e-ph coupling, leading to a large Tc in good agreement with experiment. The computed e-ph coupling constant λ is enhanced by an unprecedented factor of 5.5 as compared to DFT. Solutions of the anisotropic Eliashberg equations yield two dominant s-wave gaps – a large gap on states of rare-earth Nd d-electron and interstitial orbital characters but a small gap on those of transition-metal Ni d-electron character. The predicted two-gap s-wave superconductivity explains well tunneling experiments.

*This work was supported by U.S. DOE and NSF. Computational resources have been provided by NERSC and XSEDE.

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Presenters

  • Zhenglu Li

    • Lawrence Berkeley National Laboratory
    • University of California at Berkeley, and Lawrence Berkeley National Laboratory

Authors

  • Zhenglu Li

    • Lawrence Berkeley National Laboratory
    • University of California at Berkeley, and Lawrence Berkeley National Laboratory

  • Steven G Louie

    • University of California at Berkeley
    • University of California, Berkeley
    • University Of California, Berkeley
    • University of California at Berkeley and Lawrence Berkeley National Lab
    • University of California at Berkeley; Lawrence Berkeley National Lab
    • UC Berkeley
    • University of California at Berkeley, and Lawrence Berkeley National Laboratory
    • UC berkeley
    • Lawrence Berkeley National Laboratory
    • Physics Department, UC Berkeley and Lawrence Berkeley National Lab
    • Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory
    • LBNL & UC Berkeley