Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)

TT 11.35: Poster

Dienstag, 25. März 2003, 14:30–19:00, P2c, P2d

Kondo Enhanced Anderson Localisation — •Stefan Kettemann¹ and Mikhail Raikh² — ¹1. Institut f. Theoretische Physik, Univ. Hamburg, Hamburg 20355, Germany — ²Physics Department, Univ. of Utah, Salt Lake City 84112, USA

The electron spin scattering rate by magnetic impurities in a two–dimensional Anderson insulator governs the localization length, ξ, in the crossover region between orthogonal and unitary limits. Here we point out that, for antiferromagnetic sign of the exchange constant, the spin scattering time τ_s is itself a function of the localization length. This is due to the Kondo correlations. With τ_s being ξ-dependent, we demonstrate that the unitary regime becomes impossible when concentration of magnetic impurities, n_M, is smaller than a certain critical value, n_c. For n_M>n_c, the dependence of ξ on the dimensionless conductance g is reentrant. Namely, after crossing over from the orthogonal to the unitary dependence, the orthogonal behavior of ξ(g) is restored upon further increasing of g. Strong sensitivity of the Kondo correlations to the Zeeman energy gives rize to the dependence of ξ on a weak parallel magnetic field, which otherwise has no effect on the electronic states.