Cascade Electronic Refrigerator Using Superconducting Tunnel Junctions

Abstract

Microrefrigerators that operate in the subkelvin regime are key devices in quantum technology. A well-studied candidate, an electronic cooler using normal-metal–insulator–superconductor (N−I−S) tunnel junctions, offers substantial performance and power. However, its superconducting electrodes are severely overheated due to exponential suppression of their thermal conductance towards low temperatures, and the cooler performs unsatisfactorily—especially in powerful devices needed for practical applications. We employ a second N−I−S cooling stage to thermalize the hot superconductor at the backside of the main N−I−S cooler. Not only providing a lower bath temperature, the second-stage cooler actively evacuates quasiparticles out of the hot superconductor, especially in the low-temperature limit. We demonstrate the apparent advantage of our approach. This cascade design can also be employed to manage excess heat in other cryoelectronic devices.

Source-reported materials — not catalogue approval

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