Phase-dependent supercurrent and microwave dissipation of HgTe quantum well Josephson junctions

TL;DR

This study investigates the microwave response of HgTe quantum well Josephson junctions, revealing phase-dependent supercurrent behavior, microwave dissipation mechanisms, and the influence of interface transparency through combined experimental and theoretical analysis.

Contribution

It provides the first detailed microwave characterization of HgTe quantum well Josephson junctions, linking microwave dissipation to Andreev bound states and interface properties.

Findings

Confirmation of a small gap at phase π indicating high interface transparency

Microwave dissipation primarily due to photon-induced transitions between Andreev bound states

Gate voltage and temperature significantly affect the microwave response

Abstract

We measured the microwave response of a HgTe quantum well Josephson junction embedded into an RF SQUID loop which is inductively coupled to a superconducting resonator. The side-contacted devices studied here operate in bulk transport mode, with a separation between the superconducting contacts smaller than both the estimated carrier mean free path and superconducting coherence length. We extract the current-phase relation and the phase-dependent microwave dissipation, that, at low temperature, primarily is related to photon-induced transitions between the Andreev bound states. We study the effects of gate voltage and temperature on our devices and compare the measurements with a tight-binding model based on the Bogoliubov-de Gennes equations. A combined analysis of both microwave admittance components allows us to confirm the presence of a small gap in the Andreev bound state spectrum at phase $\pi$, indicating high interface transparency, matching our observations in DC measurements of a similar device. Our work demonstrates the versatility of microwave measurements as a tool for Josephson junction characterization and highlights the importance of the interface properties for side-contacted Josephson devices.