Magnetoresistance of p-GaAs/AlGaAs structures in the vicinity of metal-insulator transition: Effect of superconducting leads

TL;DR

This study investigates how superconducting leads influence magnetoresistance in p-GaAs/AlGaAs structures near the metal-insulator transition, revealing different behaviors in metallic and insulating samples and providing insights into tunneling and localization effects.

Contribution

It presents combined experimental and theoretical analysis of transport phenomena in semiconductor structures with superconducting contacts near the metal-insulator transition, highlighting the role of tunneling and localization.

Findings

Negative magnetoresistance peak in metallic samples due to tunneling effects

Absence of peak in insulating samples indicating different transport mechanisms

Method to distinguish weak and strong localization regimes

Abstract

Experimental and theoretical studies on transport in semiconductor samples with superconducting electrodes are reported. We focus on the samples close to metal-insulator transition. In metallic samples, a peak of negative magnetoresistance at fields lower than critical magnetic field of the leads was observed. This peak is attributed to restoration of a single-particle tunneling emerging with suppression of superconductivity. The experimental results allow us to estimate tunneling transparency of the boundary between superconductor and metal. In contrast, for the insulating samples no such a peak was observed. We explain this behavior as related to properties of transport through the contact between superconductor and hopping conductor. This effect can be used to discriminate between weak localization and strong localization regimes.