Tunneling Spectroscopy of Quasiparticle Bound States in a Spinful Josephson Junction

TL;DR

This study investigates quasiparticle bound states in a spinful Josephson junction made from InAs nanowires, revealing their evolution under magnetic fields and observing a mysterious zero bias peak.

Contribution

It provides detailed tunneling spectroscopy of sub-gap states in a spinful Josephson junction, highlighting their magnetic field dependence and the coexistence of an unexplained zero bias peak.

Findings

Sub-gap resonances evolve into Kondo-related states at high magnetic fields.

Observation of a zero bias peak of unknown origin.

Identification of Yu-Shiba-Rusinov-like states in the system.

Abstract

The spectrum of a segment of InAs nanowire, confined between two superconducting leads, was measured as function of gate voltage and superconducting phase difference using a third normal-metal tunnel probe. Sub-gap resonances for odd electron occupancy---interpreted as bound states involving a confined electron and a quasiparticle from the superconducting leads, reminiscent of Yu-Shiba-Rusinov states---evolve into Kondo-related resonances at higher magnetic fields. An additional zero bias peak of unknown origin is observed to coexist with the quasiparticle bound states.