# Dresden 2009 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 15: Correlated Electrons: Metal-Insulator Transition 2

### TT 15.1: Vortrag

### Dienstag, 24. März 2009, 09:30–09:45, HSZ 301

**Indications for a line of continuous phase transitions at finite temperatures connected with the apparent metal-insulator transition in two-dimensional disordered systems** — •Arnulf Möbius — Leibniz Institute for Solid State and Materials Research IFW Dresden, PO Box 270116, D–01171 Dresden, Germany

In a recent experiment, Lai and coworkers studied the apparent metal-insulator transition of a Si quantum well structure tuning the charge carrier concentration *n*, see [1]. They observed linear temperature dependences of the conductivity σ(*T*,*n*) around the Fermi temperature and found that the corresponding *T* → 0 extrapolation σ_{0}(*n*) exhibits a sharp bend just at the MIT.

Here, reconsidering data from [1], it is shown that this sharp bend is related to a peculiarity of σ(*T* = *const*,*n*) clearly detectable in the whole *T* range up to 4 *K*, the highest measuring temperature in [1]. Since this peculiarity seems not to be smoothed out with increasing temperature, it may indicate a sharp continuous phase transition between the regions of apparent metallic and activated conduction to be present at finite temperature. Hints from other investigations of such a behavior are discussed. Finally, a scaling analysis illuminates similarities to previous experiments and provides understanding of the shape of the peculiarity and of sharp peaks found in
d log_{10} σ / d *n* as function of *n*. Details of this study are given in [2].

[1] K. Lai, W. Pan, D.C. Tsui, S. Lyon, M. Mühlberger, and F. Schäffler, Phys. Rev. B
**75**, 033314 (2007).

[2] A. Möbius, Phys. Rev. B **77**, 205317 (2008).