Regensburg 1998 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Postersitzung III: Spin-Peierls-Systeme, Metall-Isolator-Übergang, Lokalisierung; SL: Theorie; Quantenflüssigkeiten und -kristalle; Amorphe Materialien, Tunnelsysteme; Borcarbide, Fullerene, konventionelle SL; SL dünner Filme; Experimentiertechniken

TT 21.18: Poster

Donnerstag, 26. März 1998, 15:00–18:30, D

Level Curvature Statistics in Two-Dimensional Disordered Systems — •H. Voß, I.Kh. Zharekeshev, and B. Kramer — I. Institut für Theoretische Physik, Jungiusstraße 9, D-20355 Hamburg

We study numerically statistical properties of level curvatures (second derivatives of eigenvalues with respect to a magnetic flux) in 2d disordered systems. Using finite size scaling analysis for the geometric average of the level curvatures, the scaling β-function and the disorder dependence of the localization length are determined and compared with the results obtained previously from the transfer-matrix method [1]. The weak localization correction to the Thouless energy is extracted for the orthogonal symmetry. The distribution of level curvatures exhibits a disorder-induced crossover from the random-matrix theory result (generalised Cauchy distribution)[2] to the logarithmically-normal distribution valid for the strongly localized regime. Our numerical data show the non-analyticity of the distribution at zero curvature and the connection between the branching power of the distribution and the multifractality exponent of the eigenfunctions as suggested in [3].

[1] A. Mackinnon, B. Kramer, Z. Phys. B 53, 1 (1983)

[2] J. Zakrzewski, D. Delande, Phys. Rev. E 47, 1650 (1993)

[3] V. E. Kravtsov, I. V. Yurkevich, Phys. Rev. Lett. 78, 3354 (1997)