Fast electron thermometry towards ultra-sensitive calorimetric detection

Understand

We demonstrate radiofrequency thermometry on a micrometer-sized metallic island below 100 mK.

• Our device is based on a normal metal-insulator-superconductor tunnel junction coupled to a resonator with transmission readout.
• In the first generation of the device, we achieve 90 {\mu}K/Hz^1/2 noise-equivalent temperature with 10 MHz bandwidth.
• We measure the thermal relaxation time of the electron gas in the island, which we find to be of the order of 100 {\mu}s.