Experimental determination of the quasiparticle decay length ${\xi }_{\mathrm{qp}}$ in a diffusive superconducting quantum well

We have experimentally investigated the electronic transport properties of an AlSb/InAs/AlSb quantum well, where part of the AlSb top layer has been replaced with a superconducting Nb strip. By doing a transmission experiment underneath the Nb strip and comparing the results with a model based on diffusive transport, with some of the injected electrons being Andreev reflected into holes, we can estimate the quasiparticle decay length, ${\xi }_{\mathrm{qp}}$≊50 nm, in the Nb-InAs superconducting quantum well. This decay length corresponds to an interface transparency of ${\mathit{T}}_{\mathrm{SIN}}$=0.5 between the Nb and InAs. The observed voltage dependence cannot entirely be understood within the presented model.