Quantum fluctuations and the universal criterion for the onset of superconductivity in Josephson arrays

✍ Scribed by Behzad Mirhashem; Richard A. Ferrell

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 1011 KB
• Volume: 152
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(88)90040-8

✦ Synopsis

A detailed treatment of the zero-temperature quantum fluctuations of a granular film, modeled by a regular lattice of Josephsoncoupled grains, is presented. For small grains, whose junction reactance is determined by virtual quasi-particle tunneling, mean field theory predicts a universal threshold normal state resistance, R ~F, above which zero temperature superconductivity is suppressed by phase fluctuations. Cluster calculations, which allow for the correlated fluctuations of a fraction, f<< 1, of the z neighbors of each grain, reduce R M F to R ~ -----R ~F ( 1 --3f/5Z). By exploiting analogies with the treatment of thermal fluctuations in the Ising model, we conclude that this two-term expansion remains valid for the case of physical interest, f= 1.