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

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.