Münster 1999 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 15: Postersitzung II: Elektronische Eigenschaften (1-12), Josephson-Kontakte (13-27), Heavy Fermions (28-40), Theorie HTSL (41-48), M-I-Überg
änge, Korrelierte Systeme (49-79)
TT 15.15: Poster
Mittwoch, 24. März 1999, 14:30–18:00, Foy
Quasiklassische Theorie langer diffusiver SNS-Kontakte bei endlicher Spannung — •Frank K. Wilhelm1, Andrei D. Zaikin1, and Alexander A. Golubov2 — 1Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe — 2Department of Applied Physics, University of Twente, NL-7500 AE Enschede
SNS-junctions of mesoscopic size are a peculiar realization of Josephson junctions. Although in ballistic systems, many interesting features related to coherent Andreev-reflection at finite Voltage (e.g. subharmonic gap structure, SGS) have been discovered and explained, a consistent description of diffusive junctions beyond the RSJ-Model, which does not take into account the conductance modulation induced by the proximity effect, is still missing. We apply the quasiclassical Green’s functions method to this system, including explicit time-dependence due to the AC-Josephson effect and higher harmonics generation. We show, that at relatively high voltages, the resistance of the junction is reduced by a factor ∝ RN√ETh/V where ETh=D/d2, D is the diffusion constant, d the length of the junction and RN the normal-state resistance. If one of the superconductor-normal interfaces is intransparent, the system can be described in analogy to an SS′-junction, where “S′” is only superconducting due to the proximity effect and has a gap proportional to the Thouless energy. We furthermore investigate the possibility of a remainder of SGS in the diffusive case.