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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.

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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