二维无序系统中与表观金属-绝缘体相变有关的有限温度连续相变线的指示
Indications for a line of continuous phase transitions at finite temperatures connected with the apparent metal-insulator transition in 2d disordered systems
摘要：
在最近的实验中，Lai等人[Phys.Rev.B75（2007）033314]研究了Si量子阱结构的表观金属-绝缘体转变（MIT）。通过调整载流子浓度n，他们测量了一组非常密集的n值的电导率sigma（T，n）。他们观察到σ在费米温度附近的线性T依赖性，并发现相应的T -> 0外推σ_0（n）恰好在MIT处呈现出急剧弯曲。重新考虑Lai等人的数据，这里示出了这种急剧弯曲与σ的特性（T=常数，n），这是清楚地检测到在整个T范围高达4 K，在该工作中的最高测量温度。这可能表明在有限温度下，在表观金属导电区和活化导电区之间存在急剧的连续相变。这种解释证实了无拟合的比例分析，这说明了与以前的实验相似，并提供了对dlog_{10} sigma/dn（n）中发现的特性和尖峰形状的理解。同时，标度分析揭示了表观金属态的一个奇怪特征。
英文摘要：
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.
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