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HL: Halbleiterphysik

HL 51: Hauptvortrag Ganichev

HL 51.1: Hauptvortrag

Freitag, 28. März 2003, 10:15–11:00, POT/81

Spin-galvanic effect and spin orientation induced circular photogalvanic effect in quantum well structures. — •Sergey Ganichev — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Regensburg

It is shown that a homogeneous spin polarization of electron gas drives an electric current in quantum well (QW) structures if some general symmetry requirements are met. Two effects, the spin-galvanic effect¹ and the circular photogalvanic effect² (CPGE), have been observed in n- and p-type QWs based on various semiconductor materials. These effects have in common, that the current flow is driven by an asymmetric distribution of carriers in k-space in gyrotropic systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. The spin-galvanic effect may be caused by any means of spin injection, while CPGE needs optical excitation with circularly polarized radiation. The spin-galvanic effect is due to asymmetric spin-flip scattering of spin polarized carriers and it is determined by the process of spin relaxation. The CPGE is the result of selective photoexcitation of carriers in k-space with circularly polarized light due to optical selection rules. In some optical experiments the photocurrent may represent a sum of both effects. Both effects provide methods to determine spin relaxation times.

[1] S.D. Ganichev, E.L. Ivchenko, V.V. Bel’kov, S.A. Tarasenko, M. Sollinger, D. Weiss, W. Wegscheider and W. Prettl, Nature (London) 417, 153 (2002).

[2] S.D. Ganichev, S.N. Danilov, J. Eroms, W. Wegscheider, D. Weiss, W. Prettl, and E. L. Ivchenko, Phys. Rev. Lett. 86, 4358 (2001).