Hamburg 2001 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 15: Quanten-Hall-Effekt

HL 15.5: Vortrag

Dienstag, 27. März 2001, 11:30–11:45, S16

On the break-down of scaling of the quantum Hall effect in the presence of in-homogeneities — •Josef Oswald — Institute of Physics, University of Leoben, Franz Josef Str. 18, A-8700 Leoben, Austria (e-mail: oswald@unileoben.ac.at)

The temperature dependent scaling of the quantum Hall plateau transitions is the most important basis for comparing experiment and theory. In this context an observation of a T^κ - scaling is considered as an evidence for a quantum phase transition (QPT) at zero temperature. Although the T^κ scaling has been successfully verified by many experiments, there are also quite a number of experiments where a linear scaling function (α + β· T) with a low temperature saturation is found. A major problem in comparing theory and experiment is that none of the theories so far provides results on the basis of R_xx and R_xy for realistic sample structures. Recently we developed a network model for 2D magnetotransport, which makes it possible to study in which way theoretical predictions on a microscopic level map out in R_xx and R_xy of a macroscopic sample. We demonstrate that a T^κ scaling function, which is introduced on the microscopic level of our transport model, can appear as a linear scaling function for R_xx with a significant low temperature saturation if there is a certain amount of macroscopic in-homogeneity in the carrier distribution.