Equal-Spin Andreev Reflection in Junctions of Spin-Resolved Quantum Hall Bulk State and Spin-Singlet Superconductor

TL;DR

This paper reports the experimental observation of equal-spin Andreev reflection in junctions between spin-resolved quantum Hall states and a spin-singlet superconductor, revealing potential for superconducting spintronics in semiconductor devices.

Contribution

It demonstrates the occurrence of equal-spin Andreev reflection in quantum Hall-superconductor junctions, a novel finding that advances understanding of superconducting proximity effects in spin-polarized systems.

Findings

Observation of conductance features indicating Andreev reflection

Identification of two channels of Andreev reflection involving spin-flip processes

Potential for inducing superconducting proximity gaps in quantum Hall states

Abstract

The recent development of superconducting spintronics has revealed the spin-triplet superconducting proximity effect from a spin-singlet superconductor into a spin-polarized normal metal. In addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity. Here we report experimental observation of Andreev reflection in junctions of spin-resolved quantum Hall (QH) states in an InAs quantum well and the spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap feature and two peaks on the outer side of the sub-gap feature in the QH plateau-transition regime increases. The observed structures can be explained by considering transport with Andreev reflection from two channels, one originating from equal-spin Andreev reflection intermediated by spin-flip processes and second arising from normal Andreev reflection. This result indicates the possibility to induce the superconducting proximity gap in the the QH bulk state, and the possibility for the development of superconducting spintronics in semiconductor devices.