Possible Fano effect and suppression of Andreev reflection in La$_3$Ni$_2$O$_7$

TL;DR

This paper proposes using quasiparticle tunneling and Andreev reflection measurements to distinguish pairing mechanisms in La$_3$Ni$_2$O$_7$, predicting an asymmetric Fano line shape and suppression of Andreev reflection in certain superconducting states.

Contribution

It introduces a novel approach to identify pairing scenarios in La$_3$Ni$_2$O$_7$ using tunneling and reflection techniques, highlighting the role of hybridization and interlayer coupling.

Findings

Asymmetric Fano line shape predicted due to hybridization effects.

Suppression of Andreev reflection in interlayer pairing with small interlayer hopping.

Proposes experimental methods to clarify pairing mechanisms in nickelate superconductors.

Abstract

The recently-discovered high-temperature superconductor La$_3$Ni$_2$O$_7$ under high pressure has stimulated intensive debates. Key controversies concern interlayer versus intralayer pairing scenarios and if the hybridization plays a key role in establishing the superconductivity. But experimental clarification is difficult due to the limitation of employing state-of-the-art techniques under high pressure. Here we propose that quasiparticle tunneling and Andreev reflection may provide a feasible way to distinguish different pairing scenarios. We predict that an asymmetric Fano line shape may be induced by the hybridization between the $d_{x^2-y^2}$ metallic bands and the strongly renormalized flat $d_{z^2}$ quasiparticle bands. In the superconducting state, we show that the Andreev reflection should be greatly suppressed for interlayer pairing superconductivity with a small interlayer hopping. We propose future experiments to examine these predictions and help clarify the fundamental physics of superconducting La$_3$Ni$_2$O$_7$ and other multilayer nickelate superconductors.