Non-Hermitian multiterminal phase-biased Josephson junctions

TL;DR

This paper explores non-Hermitian multi-terminal Josephson junctions, revealing exceptional points influenced by superconducting phases and dissipation, with implications for topological superconducting phenomena.

Contribution

It introduces the concept of exceptional points in multi-terminal Josephson junctions driven by phase differences and non-Hermiticity, highlighting their topological protection and tunability.

Findings

Exceptional points depend on superconducting phases and non-Hermiticity.

Stable lines and surfaces of exceptional points are topologically protected.

Dissipation can enhance supercurrents via hybridized Andreev bound states.

Abstract

We study non-Hermitian Josephson junctions formed by multiple superconductors and discover the emergence of exceptional points entirely determined by the interplay of the distinct superconducting phases and non-Hermiticity due to normal reservoirs. In particular, in Josephson junctions with three and four superconductors, we find stable lines and surfaces of exceptional points protected by non-Hermitian topology and highly tuneable by the superconducting phases. We also discover that, in Josephson junctions formed by laterally coupled superconductors, exceptional points can result from hybridized Andreev bound states and lead to the enhancement of supercurrents controlled by dissipation. Our work unveils the potential of multi-terminal Josephson junctions for realizing higher dimensional topological non-Hermitian superconducting phenomena.