Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 19: Transport - Nanoelectronics I: Spintronics and Magnetotransport

TT 19.2: Talk

Monday, March 7, 2005, 10:15–10:30, TU H3027

Andreev magnetotransport in low-dimensional semiconductors: Application to spin detection — •Grigory Tkachov and Klaus Richter — Institute for Theoretical Physics, Regensburg University, 93040 Regensburg, Germany

We investigate a possibility of using the superconducting proximity effect for detecting spin of transport carriers in two-dimensional electron systems (2DES), a problem closely related to the ongoing work on spin injection in semiconductors. The proximity effect is described within a ballistic approach taking into account the formation of an induced minigap in the excitation spectrum of a 2DES in planar superconductor/2DES contacts, which leads to enhanced Andreev reflection and the excess conductance at low bias voltages in agreement with experiments [1]. We show that in a 2DES subject to an in-plane magnetic field the Zeeman splitting of the proximity-modified states gives rise to spin-selective Andreev transport as opposed to conventional tunnel junctions where the spin splitting affects only the quasiparticle current [2]. Our model of spin-dependent Andreev reflection also accounts for a diamagnetic effect of the screening supercurrent induced by the magnetic field.

[1] C. Nguyen, H. Kroemer, and E.L. Hu, Phys. Rev. Lett. 69, 2847 (1992); F. Rahman and T. J. Thornton, Superlat. Microstr., 25 767 (1999); J. Eroms, M. Tolkiehn, D. Weiss, U. Rössler, J. DeBoeck, S. Borghs, Europhys. Lett. 58, 569 (2002).

[2] R. Meservey, P. M. Tedrow, and P. Fulde, Phys. Rev. Lett. 25, 1270 (1970); R. Meservey and P. M. Tedrow, Phys. Reports 238, 173 (1994).