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TT: Fachverband Tiefe Temperaturen

TT 34: Superconductivity: Heterostructures

TT 34.1: Hauptvortrag

Dienstag, 1. April 2014, 11:15–11:45, HSZ 201

Giant Thermopower in the Emerging Field of Super-Spintronics — •Matthias Eschrig — Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom

Thermoelectric effects in metals and superconductors are usually negligibly small as they require a strongly asymmetric density of states. Thus, relatively little attention has been paid to these effects so far in the new emerging field of super-spintronics. This field combines the advantages of control of spin as basic principle in spintronics with that of macroscopic quantum interference, a hallmark of superconductivity. At the same time, non-local transport has been studied during the past decade in connection with so-called crossed Andreev reflection in a number of pivotal experiments. I will discuss how the idea of non-local transport has been generalised to include thermal currents in superconducting spintronics devices [1]. Surprisingly, it turns out that a dramatic enhancement of thermoelectric effects can be achieved when combining spin-dependent scattering phases with spin-filtering effects in superconductor-ferromagnet heterostructures. Thermopowers of the order of 100 µV/K can be achieved. We study a non-local setup with three terminals (two ferromagnetic, one superconducing), and show that a nonlocal version of the Onsager symmetry relations holds. We calculate all thermodynamic coefficients in diffusive as well as ballistic structures, and include non-equilibrium distribution functions as well as singlet-triplet mixing in the superconducting region.
P. Machon, M. Eschrig, W. Belzig, PRL 110, 047002 (2013).