Granular aluminum nano-superconducting quantum interference device

Granular aluminum (grAl) is an applied quantum material. We present nano-superconducting quantum interference devices (nanoSQUIDs) based on grAl thin films. These devices exhibit non-hysteretic behavior, allowing conventional SQUID readout down to temperatures well below the critical temperature as well as detection properties comparable to those of Dayem bridge-based devices of greater complexity. Despite being much longer than the coherence length, the current-phase relation of these grAl constrictions appears to be single valued at least down to half their critical temperature. This suggests that grAl thin films should be described as a network of inter-grain Josephson junctions.