Superconducting tunnel-junction refrigerator
The dc current through an S/sub 1/-S/sub 2/ tunnel junction, with ..delta../sub 2/ greater than ..delta../sub 1/, when biased with eV<..delta../sub 1/+..delta../sub 2/, will lower the energy in S/sub 1/. This energy reduction will be shared by the phonons and electrons. This device is shown to be analogous to a thermoelectric refrigerator with an effective Peltier coefficient ..pi..* approx. ..delta../sub 1//e. Tunneling calculations yield the cooling power P/sub c/, the electrical power P/sub e/ supplied by the bias supply, and the cooling efficiency eta=P/sub c//P/sub e/. The maximum cooling power is obtained for eV= +- (..delta../sub 2/-..delta../sub 1/) and t/sub 1/=T/sub 1//T/sub c/1 approx. 0.9. Estimates are made of the temperature difference T/sub 2/-T/sub 1/ achievable in Al-Pb and Sn-Pb junctions with an Al/sub 2/O/sub 3/ tunneling barrier. The performance of this device is shown to yield a maximum cooling efficiency eta approx. = ..delta../sub 1//(..delta../sub 2/-..delta../sub 1/) which can be compared with that available in an ideal Carnot refrigerator of eta=T/sub 1//(T/sub 2/-T/sub 1/). The development of a useful tunnel-junction refrigerator requires a tunneling barrier with an effective thermal conductance per unit area several orders of magnitude less than that provided by the A1/sub 2/O/sub 3/ barrier in the Al-Pb and Sn-Pb systems.
- Research Organization:
- Physics Department, University of Virginia, Charlottesville, Virginia 22901
- OSTI ID:
- 5667255
- Journal Information:
- Phys. Rev., B: Condens. Matter; (United States), Vol. 21:5
- Country of Publication:
- United States
- Language:
- English
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