Conductance oscillations with magnetic field of a two-dimensional electron gas-superconductor junction

TL;DR

This paper investigates how surface roughness affects conductance oscillations in a 2DEG-superconductor junction under magnetic field, providing a model that aligns with experimental observations and explains the suppression of oscillations due to interface disorder.

Contribution

The study introduces a theoretical approach incorporating surface roughness to explain conductance oscillations and their suppression in 2DEG-superconductor interfaces under magnetic fields.

Findings

Surface roughness qualitatively explains conductance oscillation visibility.

Disorder at the interface suppresses conductance oscillations.

Higher harmonics are less visible in experiments, consistent with the model.

Abstract

We find the current voltage characteristics of a 2DEG-S interface in magnetic field taking into account the surface roughness. Typically in experiments $L/2R_c\gtrsim 3$, where $L$ is the surface length and $R_c$ is the cyclotron radius. The conductance behaves in experiments usually as $G=g_0+g_1\cos(2\pi\nu+\delta_1)$; higher harmonics, $g_2\cos(4\pi\nu+\delta_2),...$, are hardly seen. Theories based on the assumption of the interface perfectness can hardly describe qualitatively the visibility of the condctance oscillations and the amplitudes of the harmonics: they predict $g_1\sim g_2\sim g_3,...$. Our approach with the surface roughness qualitatively agrees with experiments. It is shown how a disorder at a 2DEG-S interface suppresses the conductance oscillations with $\nu$.