Indications for a line of continuous phase transitions at finite temperatures connected with the apparent metal-insulator transition in 2d disordered systems

Abstract

In a recent experiment, Lai et al. [Phys. Rev. B 75 (2007) 033314] studied the apparent metal-insulator transition (MIT) of a Si quantum well structure. Tuning the charge carrier concentration n, they measured the conductivity sigma(T,n) for a very dense set of n values. They observed linear T dependences of sigma around the Fermi temperature and found that the corresponding T -> 0 extrapolation sigma_0(n) exhibits a sharp bend just at the MIT. Reconsidering the data by Lai et al., it is shown here that this sharp bend is related to a peculiarity of sigma(T=const.,n), which is clearly detectable in the whole T range up to 4 K, the highest measuring temperature in that work. It may indicate a sharp continuous phase transition between the regions of apparent metallic and activated conduction to be present at finite temperature. This interpretation is confirmed by a scaling analysis without fit, which illuminates similarities to previous experiments and provides understanding of the shape of the peculiarity and of sharp peaks found in dlog_{10}sigma/dn(n). Simultaneously, the scaling analysis uncovers a strange feature of the apparent metallic state.

4 pages, 4 figures, accepted for Proceedings EP2DS-18 in Physica E; substantially extends detailed arguments presented in arXiv:0712.0992

References in corpus (5)

• Metal-insulator transition in two-dimensional electron systems
• Unconventional critical behaviour in a quasi-two-dimensional organic conductor
• Linear temperature dependence of conductivity in Si two-dimensional electrons near the apparent metal-to-insulator transition
• Metallic conduction, apparent metal-insulator transition and related phenomena in two-dimensional electron liquid
• Indications for sharp continuous phase transitions at finite temperatures connected with the apparent metal-insulator transition in two-dimensional disordered systems