Condensed Matter Physics Seminar

Thursday, September 21, 2000, 2 p.m.
Plant Sciences Building, Room 1130

Theory of Andreev Reflection at the Superconductor-Ferromagnet Boundary

Igor Mazin

(Naval Research Laboratory, Washington, DC)

Abstract:  Andreev reflection (AR) at a boundary between a ferromagnet and a superconductor is a new and promising method for probing the degree of spin polarization (DSP) at the Fermi level.  Unfortunately, as with all others methods, it is not clear which combination of the density of states, Fermi velocity, and possibly additional matrix elements, defines the measured DSP.  A further complication in case of AR is the lack of a complete theory, taking into account evanescent wave matching the Cooper pairs for spin-forbidden AR, even in the ballistic regime, and lack of any theory in the diffusive regime.  Furthermore, nearly all theoretical work on this subject makes use of the one-parabolic-band model with a k-independent exchange splitting.  While theoretically appealing, this model bears no relevance to the processes in the real d-electron ferromagnets. Thus the requested theory must also be able to handle arbitrary bands and arbitrary Fermi surface geometry in both spins, as well as in the superconducting lead.  I will present such a theory for both ballistic and diffusive regimes, making particular emphasis on the role of the Fermi surface geometry and on some practical aspects of processing results of the AR measurements.

Host: Victor Yakovenko

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