Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 7: SC: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence

TT 7.1: Vortrag

Montag, 22. März 2010, 14:00–14:15, H20

Spin-dependent boundary conditions for isotropic superconducting Green’s functions — •Wolfgang Belzig¹, Audrey Cottet², Daniel Huertas-Hernando³, and Yuli Nazarov⁴ — ¹Fachbereich Physik, Universität Konstanz, Konstanz, Germany — ²Ecole Normale Supérieure, Laboratoire Pierre Aigrain, Paris, France — ³Department of Physics, Norwegian University of Science and Technology,Trondheim, Norway — ⁴Kavli Institute of NanoScience, Delft University of Technology, Delft, The Netherlands

The quasiclassical theory of superconductivity provides the most successful description of diffusive hetero- structures comprising superconducting elements, namely, the Usadel equations for isotropic Green’s functions. Since the quasiclassical and isotropic approximations break down close to interfaces, the Usadel equations have to be supplemented with boundary conditions for isotropic Green’s functions (BCIGF), which are not derivable within the quasiclassical description. For a long time, the BCIGF were available only for spin- degenerate tunnel contacts, which posed a serious limitation on the applicability of the Usadel description to modern structures containing ferromagnetic elements. We close this gap and derive spin- dependent BCIGF for a contact encompassing superconducting and ferromagnetic correlations [1]. This finally justifies several simplified versions of the spin-dependent BCIGF, which have been used in the literature so far [2].

[1] A. Cottet, D. Huertas-Hernando, W. Belzig and Yu. V. Nazarov, Phys. Rev. B 80, 184511 (2009)

[2] D. Huertas-Hernando, Yu. V. Nazarov, W. Belzig, Phys. Rev. Lett. 88, 047003 (2002)