Nonequilibrium Andreev bound states population in short superconducting junctions coupled to a resonator

TL;DR

This paper investigates the nonequilibrium population of Andreev bound states in short superconducting junctions within a dc-SQUID, considering phase fluctuations, quasiparticle distributions, and photon irradiation effects, comparing conventional and topological cases.

Contribution

It provides a detailed analysis of ABS occupations in short superconducting junctions, including the effects of phase fluctuations, quasiparticle distributions, and external irradiation, with a comparison between conventional and topological junctions.

Findings

Different occupation patterns for conventional and topological junctions.

Impact of phase fluctuations and quasiparticle temperature on ABS populations.

Photon irradiation can induce nonequilibrium occupations of ABS.

Abstract

Inspired by recent experiments, we study a short superconducting junction of length $L\ll \xi$ (coherence length) inserted in a dc-SQUID containing an ancillary Josephson tunnel junction. We evaluate the nonequilibrium occupation of the Andreev bound states (ABS) for the case of a conventional junction and a topological junction, with the latter case of ABS corresponding to a Majorana mode. We take into account small phase fluctuations of the Josephson tunnel junction, acting as a damped LC resonator, and analyze the role of the distribution of the quasiparticles of the continuum assuming that these quasiparticles are in thermal distribution with an effective temperature different from the environmental temperature. We also discuss the effect of strong photon irradiation in the junction leading to a nonequilibrium occupation of the ABS. We systematically compare the occupations of the bound states and the supercurrents carried by these states for conventional and topological junctions.