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TT: Fachverband Tiefe Temperaturen
TT 29: Superconductivity: Mechanisms, Phase Diagram, Competing Order
TT 29.10: Vortrag
Donnerstag, 28. Februar 2008, 12:15–12:30, H 3010
Mesoscopic effects in small superconducting grains: a semiclassical approach to BCS theory — Antonio M Garcia-Garcia2, •Juan Diego Urbina1, Emil Yuzbashyan3, Klaus Richter1, and Boris Altshuler4 — 1nstitut für Theoretische Physik, Universität Regensburg, 93053 Regensburg — 2Physics Department, Princeton University, Princeton, New Jersey 08544, USA — 3Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08544, USA — 4Physics Department, Columbia University, 538 West 120th Street, New York, NY 10027, USA
We present a novel approach to mesoscopic superconductivity based on a semiclassical approximation for both the density of states and the interaction matrix elements [1] entering the BCS gap equation. In this way, the discretness of the single-particle spectra and the inhomogeneity of the single particle eigenfunctions are included consistenly as mesoscopic fluctuations around the bulk values. We apply the theory to 3D cubic grains, finding good agreement with exact numerical calculations. For grains with irregular shape we predict a novel dependence of the gap with the excitation energy, present in an experimentally relevant region of parameters [2].
[1] J. D. Urbina and K. Richter Phys. Rev. Lett. 97, 214101 (2006).
[2] A. M. Garcia-Garcia, J. D. Urbina, Emil Yuzbashyan, K. Richter and B.L Altshuler cond-mat/0710.2286 (2006).