Quartet Tomography in Multiterminal Josephson Junctions

TL;DR

This paper explores the detection and characterization of quartets in multiterminal Josephson junctions, revealing their ubiquity and proposing methods to identify them through current-phase relations and Andreev bound state spectra.

Contribution

It introduces a rigorous approach to extract quartet contributions and links their presence to Andreev bound state hybridization in hybrid superconducting systems.

Findings

Quartets are common in multiterminal Josephson junctions.

A method to identify quartets via ABS spectra is proposed.

Spectroscopic data suggests the presence of quartets in InAs/Al junctions.

Abstract

We investigate the detection of quartets in hybrid multiterminal Josephson junctions. Using simple models of quantum dots coupled to superconducting leads, we find that quartets are ubiquitous and show how to rigorously extract their contribution to the current-phase relation (CPR). We also demonstrate that quartets are closely related to the hybridization of Andreev bound states (ABSs) in these systems and propose a method to identify quartets directly in ABS spectra. We illustrate our method by analyzing the spectroscopic measurements of the ABS spectrum in a three-terminal Josephson junction realized in an InAs/Al heterostructure. Our analysis strongly suggests the existence of quartets in the studied hybrid system.