Quantum Andreev effect in 2D HgTe/CdTe quantum well-superconductor systems

TL;DR

This paper predicts a universal, robust quantized Andreev reflection in 2D HgTe/CdTe quantum well-superconductor systems, leading to conductance quantization, independent of system parameters or disorder.

Contribution

It introduces the concept of a quantum Andreev effect with quantized AR coefficient, highlighting its universality and robustness in hybrid systems.

Findings

Quantized Andreev reflection with AR coefficient equal to one.

Conductance exhibits a quantized plateau below the superconductor gap.

The effect is independent of system parameters and disorder.

Abstract

The Andreev reflection (AR) in 2D HgTe/CdTe quantum well-superconductor hybrid systems is studied. A quantized AR with AR coefficient equal to one is predicted, which is due to the multi-Andreev reflection near the interface of the hybrid system. Importantly, this quantized AR is not only universal, i.e., independent of any system parameters and quality of the coupling of the hybrid system, it is also robust against disorder as well. As a result of this quantum Andreev effect, the conductance exhibits a quantized plateau when the external bias is less the superconductor gap.