Regensburg 2000 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 22: Postersitzung III: Supraleitende Anwendungen (1-4) Massive HTSL, Bandleiter, Filme (5-26), Transport in HTSL (27-30), Elektronenstruktur in Supraleitern (31-43), Borkarbide (44-50), Quantenphasen- und Metall-Isolator-Überg
änge (51-69)
TT 22.61: Poster
Donnerstag, 30. März 2000, 14:00–17:30, A
Critical properties of the metal-insulator transition in anisotropic systems — •F. Milde, R.A. Römer, and M. Schreiber — Institut für Physik, Technische Universität, D-09107 Chemnitz
We study the three dimensional Anderson model of localization with anisotropic hopping, i.e., weakly coupled chains and weakly coupled planes. This model, particulary the chain case, is related to experiments in which uniaxial stress is applied to tune doped semiconductors accross the metal-insulator transition (MIT). In our extensive numerical study we identify and characterize the MIT using energy-level statistics (ELS) and the transfer-matrix method (TMM). The values of the critical disorder Wc obtained with the two methods are consistent with results of previous studies, including multifractal analysis of the wave functions. Wc decreases from its isotropic value with a power law as a function of anisotropy. Using high accuracy data for large system sizes we estimate the critical exponent as ν=1.62±0.07 from TMM and ν=1.45±0.2 from ELS. This is in agreement with its value in the isotropic case and in other models of the orthogonal universality class. The system size independent level statistics at the transition changes with increasing anisotropy from its isotropic form towards the Poisson statistics.