Possible Fano Effect and Suppression of Andreev Reflection in La₃Ni₂O₇

The recently discovered high-temperature superconductor La₃Ni₂O₇ under high pressure has sparked considerable debate. Central controversies revolve around whether interlayer or intralayer pairing mechanisms dominate and whether hybridization plays a crucial role in establishing superconductivity. However, experimental clarification remains challenging due to the limitations of state-of-the-art techniques under high-pressure conditions. Here, we propose that quasiparticle tunneling and Andreev reflection could offer practical methods to differentiate pairing scenarios. Specifically, we predict that hybridization between the d_x^2-y^2 metallic bands and the strongly renormalized flat d_z^2 quasiparticle bands may induce an asymmetric Fano line shape. In the superconducting state, we show that Andreev reflection would be significantly suppressed in interlayer pairing superconductivity with limited interlayer hopping. We recommend future experiments to test these predictions and shed light on the fundamental physics of superconducting La₃Ni₂O₇ and other multi-layer nickelate superconductors.