Directional electron-filtering at a superconductor-semiconductor interface

TL;DR

This paper investigates how electronic band-structure differences at superconductor-semiconductor interfaces create a directional momentum-filter, influencing transport properties and mode selectivity, especially in low-carrier density semiconductors.

Contribution

It introduces a microscopic analysis of mode-selectivity and directional filtering at superconductor-semiconductor interfaces without geometric confinement.

Findings

Electronic band-structure differences induce mode-selectivity.

Transport dominated by Andreev reflection with low back-scattering.

Gate-tunable electronic properties affect transport behavior.

Abstract

We evaluate the microscopically relevant parameters for electrical transport of hybrid superconductor-semiconductor interfaces. In contrast to the commonly used geometrically constricted metallic systems, we focus on materials with dissimilar electronic properties like low-carrier density semiconductors combined with superconductors, without imposing geometric confinement. We find an intrinsic mode-selectivity, a directional momentum-filter, due to the differences in electronic band-structure, which creates a separation of electron reservoirs each at the opposite sides of the semiconductor, while at the same time selecting modes propagating almost perpendicular to the interface. The electronic separation coexists with a transport current dominated by Andreev reflection and low elastic back-scattering, both dependent on the gate-controllable electronic properties of the semiconductor.