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Leggett, Anthony J. Fisher, Matthew Paul Alejandro 2011-06-03T15:05:02Z 2011-06-03T15:05:02Z 10000-01-01 1986 This thesis is devoted to a study of the quantum dynamics of small Josephson junctions. Of interest are those features of the junction's behavior which depend explicitly on the quantum mechanical nature of the phase difference <1> between the superconductors. In Chapters I and IT several calculations are described which focus on the junction's DC resistance. A fully quantum mechanical Hamiltonian is employed which incorporates the dissipative effects due to the unpaired electrons by coupling to a bath of harmonic oscillators. It is shown that the model exhibits a novel zero temperature phase transition as a function of the strength of the dissipation. In the low dissipation regime the phase is free to tunnel quantum mechanically and the junction's resistance is finite; in response to an external current, tunnelling induces successive 21t phase slips leading to a finite voltage state. In contrast, in the high dissipation regime, tunnelling is suppressed and the junction behaves as a superconductor carrying current with no resistive losses. In Chapters m and N these results are applied in an attempt to explain the recent observation that in ultra-thin Sn films there is apparently a universal normal state sheet resistance above which superconductivity cannot be established. The ftlms are modelled as a random array of superconducting islands linked together by small Josephson junctions. By combining this picture with the calculations for the single junction behavior, a natural explanation for the observed data is presented. Specifically, it is demonstrated that when the sheet resistance is larger than the quantum of resistance, Rq=h/4e2 , quantum tunnelling of the phase between neighboring islands drives the film normal. This value of the universal resistance· agrees quantitatively with the experiment Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-03T15:05:02Z No. of bitstreams: 1 1986_fisher.pdf: 7981111 bytes, checksum: f8c34b2020d99c495dbaa7bb4da7403f (MD5) Made available in DSpace on 2011-06-03T15:05:02Z (GMT). No. of bitstreams: 1 1986_fisher.pdf: 7981111 bytes, checksum: f8c34b2020d99c495dbaa7bb4da7403f (MD5) Previous issue date: 1986 Restriction data tranferred 2014-07-01T11:12:40-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-03T15:05:02Z Item is restricted indefinitely. Thesis U of I Only 978711 http://hdl.handle.net/2142/25250 en 1986 Matthew Paul Alejandro Fisher quantum dynamics small Josephson functions superconductors Quantum dynamics of small Josephson junctions: an application to superconductivity in granular films Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.