Minimal two band model and experimental proposals to distinguish pairing mechanisms of the high-T$_c$ superconductor La$_3$Ni$_2$O$_7$

TL;DR

This paper develops a minimal two-band model for La$_3$Ni$_2$O$_7$ to differentiate pairing mechanisms of high-T$_c$ superconductivity through specific experimental tests involving electric fields.

Contribution

It introduces a minimal two-band model matching experimental Fermi-surface data and proposes experimental protocols to distinguish pairing mechanisms in La$_3$Ni$_2$O$_7$.

Findings

Different pairing mechanisms respond distinctly to perpendicular electric fields.

The model reproduces observed Fermi-surface topology.

Proposed experiments can identify the dominant pairing mechanism.

Abstract

The discovery of high-T$_c$ superconductivity in La$_3$Ni$_2$O$_7$ has opened the door to a new route to high temperature superconductivity, distinct from that in cuprates and iron-based materials. Yet, despite intense recent activity, we lack experimentally testable protocols for distinguishing between different pairing scenarios. In this Letter, we construct a minimal two-band model that reproduces the Fermi-surface topology observed in recent ARPES measurements and DFT calculations, and we analyze superconductivity arising from two distinct pairing mechanisms. We show that these mechanisms yield sharply different responses to an applied perpendicular electric field. Thus, La$_3$Ni$_2$O$_7$ offers the unique opportunity to cleanly distinguish between different pairing scenarios. Finally, we propose three concrete experimental proposals designed to distinguish these scenarios and thereby identify the pairing mechanism most relevant to the real material.