Dresden 2009 – wissenschaftliches Programm
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 . They observed linear temperature dependences of the conductivity σ(T,n) around the Fermi temperature and found that the corresponding T → 0 extrapolation σ0(n) exhibits a sharp bend just at the MIT.
Here, reconsidering data from , 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 . 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 log10 σ / d n as function of n. Details of this study are given in .
 K. Lai, W. Pan, D.C. Tsui, S. Lyon, M. Mühlberger, and F. Schäffler, Phys. Rev. B 75, 033314 (2007).
 A. Möbius, Phys. Rev. B 77, 205317 (2008).