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

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of a two-dimensional electron gas (2DEG) present in an AlSb/InAs/AlSb quantum well, where part of the toplayer has been replaced by a superconducting Nb strip, with an energy gap ${\Delta }_0$.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-Büttiker 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 ${\Delta }_{\text{eff}}=0.97{\Delta }_0=0.83\text{meV}$.

Revtex, 3 PostScript figures