Superconducting junctions with flat bands

TL;DR

This paper investigates the unique properties of flat-band superconductor junctions, revealing how their supercurrent behavior and Andreev reflection differ from conventional junctions, with implications for flat-band electronic systems.

Contribution

It introduces a detailed analysis of flat-band superconductor junctions, highlighting novel effects on supercurrent and Andreev reflection not seen in traditional systems.

Findings

Critical Josephson current inversely proportional to pair potential

Quantum geometric contribution affects supercurrent even in normal state

Bound states significantly influence Andreev reflection

Abstract

We analyze the properties of flat-band superconductor junctions that behave differently from ordinary junctions containing only metals with Fermi surfaces. In particular, we show how in the tunneling limit the critical Josephson current between flat-band superconductors is inversely proportional to the pair potential, how the quantum geometric contribution to the supercurrent contributes even in the normal state of a flat-band weak link, and how Andreev reflection is strongly affected by the presence of bound states. Our results are relevant for analyzing the superconducting properties of junctions involving electronic systems with flat bands.