1. Efficient electronic cooling above 2 K by niobium-based superconducting tunnel junctions
- Author
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Hätinen, J., Ronzani, A., Loreto, R. P., Mykkänen, E., Kemppinen, A., Viisanen, K., Rantanen, T., Geisor, J., Lehtinen, J., Ribeiro, M., Kaikkonen, J-P., Prakash, O., Vesterinen, V., Förbom, W., Mannila, E. T., Kervinen, M., Govenius, J., and Prunnila, M.
- Subjects
Condensed Matter - Superconductivity - Abstract
Replacing the bulky cryoliquid-based cooling stages of cryoenabled instruments by chip-scale refrigeration is envisioned to disruptively reduce the system size similar to microprocessors did for computers. Electronic refrigerators based on superconducting tunnel junctions have been anticipated to provide a solution, but reaching the necessary above the 1-K operation temperature range has remained a goal out of reach for several decades. We show efficient electronic refrigeration by Al-AlO$_x$-Nb superconducting tunnel junctions starting from bath temperatures above 2 K. The junctions can deliver electronic cooling power up to approximately mW/mm$^2$, which enables us to demonstrate tunnel-current-driven electron temperature reduction from 2.4 K to below 1.6 K (34% relative cooling) against the phonon bath. Our work shows that the key material of integrated superconducting circuits - niobium - enables powerful cryogenic refrigerator technology. This result is a prerequisite for practical cryogenic chip-scale refrigerators and, at the same time, it introduces a new electrothermal tool for quantum heat-transport experiments.
- Published
- 2024
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