Shiba Bound States across the mobility edge in doped InAs nanowires

TL;DR

This study investigates how doping-induced localization and delocalization in InAs nanowires affect superconducting subgap states, revealing a transition from quasiparticle co-tunneling to Shiba states and Andreev resonances.

Contribution

It demonstrates the evolution of subgap states across the mobility edge in doped InAs nanowires, linking electronic phase transitions to superconducting spectral features.

Findings

Localization reduces excited level amplitudes and widths.

Shiba bound states emerge near the mobility edge.

Single Andreev resonances appear in the metallic regime.

Abstract

We present a study of Andreev Quantum Dots (QDots) fabricated with small-diameter (30 nm) Si-doped InAs nanowires where the Fermi level can be tuned across a mobility edge separating localized states from delocalized states. The transition to the insulating phase is identified by a drop in the amplitude and width of the excited levels and is found to have remarkable consequences on the spectrum of superconducting SubGap Resonances (SGRs). While at deeply localized levels, only quasiparticles co-tunneling is observed, for slightly delocalized levels, Shiba bound states form and a parity changing quantum phase transition is identified by a crossing of the bound states at zero energy. Finally, in the metallic regime, single Andreev resonances are observed.