Magnetotransport properties of thin Josephson junctions for spectroscopic applications in the presence of large magnetic fields

Abstract

We study thin aluminum Josephson tunnel junctions for spectroscopic applications in high in-plane magnetic fields. These devices, fabricated via a double-angle evaporation process, feature junction stack thickness below 30 nm and lateral dimensions between 80 and 900 nm. Measurements of current–voltage characteristics at 25 mK reveal insights into the Josephson supercurrent, superconducting gap, and inelastic Cooper pair tunneling peaks, driven by the interplay between the ac-Josephson effect and frequency-dependent junction environment impedance. The magnetic field modulation of the Josephson current follows a Fraunhofer pattern for magnetic fields exceeding 1 T, while an on-chip LC electromagnetic mode is probed through the inelastic tunneling peak at fields up to 1.3 T. These findings highlight the robustness of thin aluminum junctions for probing low-energy excitations, such as Andreev bound states, under high magnetic fields, and their potential in quantum device integration and topological state exploration.