Josephson inductance as a probe for highly ballistic semiconductor-superconductor weak links

TL;DR

This paper introduces a method using Josephson inductance measurements to probe highly ballistic semiconductor-superconductor weak links, revealing detailed properties like transparency and current-phase relation without phase bias.

Contribution

The study demonstrates a novel approach to analyze ballistic Josephson junctions through inductance measurements, providing insights into device transparency and supercurrent interference effects.

Findings

Near-unity transparency $ar{ au}=0.94$ was achieved.

Inductance measurements reveal current-phase relation directly.

Supercurrent interference in inductance is highly sensitive to transparency.

Abstract

We present simultaneous measurements of Josephson inductance and DC transport characteristics of ballistic Josephson junctions based upon an epitaxial Al-InAs heterostructure. The Josephson inductance at finite current bias directly reveals the current-phase relation. The proximity-induced gap, the critical current and the average value of the transparency $\bar{\tau}$ are extracted without need for phase bias, demonstrating, e.g.,~a near-unity value of $\bar{\tau}=0.94$. Our method allows us to probe the devices deeply in the non-dissipative regime, where ordinary transport measurements are featureless. In perpendicular magnetic field the junctions show a nearly perfect Fraunhofer pattern of the critical current, which is insensitive to the value of $\bar{\tau}$. In contrast, the signature of supercurrent interference in the inductance turns out to be extremely sensitive to $\bar{\tau}$.