Experimental determination of the quasi-particle decay length $\xi_{\text{Sm}}$ in a superconducting quantum well

TL;DR

This study experimentally measures the decay length of quasi-particles in a superconducting quantum well, providing insights into interface transparency and energy gap characteristics relevant for quantum device applications.

Contribution

It introduces an experimental method to determine the quasi-particle decay length in a superconducting quantum well using transport measurements and theoretical modeling.

Findings

Decay length $\xi_{ ext{Sm}} ext{ extasciitilde }100~ ext{nm}$

Interface transparency $T_{ ext{SIN}}=0.7$

Effective energy gap $\xi_{ ext{eff}}=0.83~ ext{meV}$

Abstract

We have investigated experimentally the electronic transport properties of a two-dimensional electron gas (2DEG) present in an AlSb/InAs/AlSb quantum well, where part of the toplayer has been replaced by a superconducting Nb strip, with an energy gap $\Delta_0$. By measuring the lateral electronic transport underneath the superconductor, and comparing the experimental results with a model based on the Bogoliubov-de Gennes equation and the Landauer-B\"uttiker formalism, we obtain a decay length $\xi_{\text{Sm}} \approx 100~\text{nm}$ for electrons. This decay length corresponds to an interface transparency $T_{\text{SIN}}=0.7$ between the Nb and InAs. Using this value, we infer an energy gap in the excitation spectrum of the SQW of $\Delta_{\text{eff}} = 0.97 \Delta_0 = 0.83~\text{meV}$.