Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 25: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 25.3: Vortrag

Mittwoch, 27. Februar 2008, 14:30–14:45, H 3010

Non-local Andreev reflection in superconducting quantum dots — •Dmitry Golubev and Andrei Zaikin — Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021, Karlsruhe, Germany

With the aid of the Keldysh technique we develop a microscopic theory of non-local electron transport in three-terminal NSN structures consisting of a chaotic superconducting quantum dot attached to one superconducting and two normal electrodes. Our theory fully accounts for non-equilibrium effects and disorder in a superconducting terminal. We go beyond perturbation theory in tunneling and derive a general expression for the system conductance matrix which remains valid in both weak and strong tunneling limits. We demonstrate that the proximity effect yields a decrease of crossed Andreev reflection (CAR). Beyond weak tunneling limit the contribution of CAR to the non-local conductance does not cancel that of direct electron transfer between two normal terminals. We argue that temperature dependence of the non-local resistance of NSN devices is determined by the two competing processes -- Andreev reflection and charge imbalance -- and it has a pronounced peak occurring at the crossover between these two processes. This behavior is in a good agreement with recent experimental observations.