High-performance amorphous superconducting rhenium films by e-beam evaporation

We present electron beam evaporation of rhenium films on room-temperature substrates. The films are shown to be amorphous and achieve a record-high critical temperature for rhenium—exceeding 7 K at the midpoint of the transition—alongside a high critical current density of 5000 A/mm2 and critical fields above 10 T. Terahertz spectroscopy reveals a Bardeen–Cooper–Schrieffer-like character of superconductivity with a zero-temperature energy gap of approximately 2 meV and subgap optical conductivity. Despite being friable, the films are stable and compatible with lift-off processes that opens the capabilities for superconducting device applications.