Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 48: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Vortices

TT 48.7: Talk

Friday, March 30, 2012, 11:00–11:15, H 2053

Transport properties of a Josephson junction coupled to the dynamics of a nanomagnet — •Cecilia Holmqvist¹, Wolfgang Belzig¹, and Mikael Fogelström² — ¹Fachbereich Physik, Universität Konstanz, 78457 Konstanz — ²Department of Microtechnology and Nanoscience - MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden

The interplay between superconductivity and ferromagnetism in nanoscale junctions may lead to interesting effects that could be utilized in spintronics devices. Here, we present a theoretical study of a superconducting point contact coupled to a nanomagnet. The magnetization of the nanomagnet is brought into precession by an external magnetic field. The coupling between the Josephson effect and the magnetization precession modifies the current-phase relation [1]. Additionally, the critical current is enhanced at finite temperatures due to coupling between the continuum of states and the Andreev levels. The spin-dependent Andreev scattering also generates an ac spin current, that decays on the length scale of the superconducting coherence length. For a voltage-biased Josephson junction coupled to a precessing spin, the interplay between spin-scattering processes and multiple Andreev reflection, characterized by the Larmor and Josephson frequencies, respectively, leads to a modification of the current-voltage characteristics as well as the spin transport properties.
C. Holmqvist, S. Teber, and M. Fogelström, Phys. Rev. B 83, 104521 (2011)