二维无序系统中与表观金属-绝缘体相变有关的有限温度下尖锐连续相变的指示
Indications for sharp continuous phase transitions at finite temperatures connected with the apparent metal-insulator transition in two-dimensional disordered systems
摘要：
在最近的实验中，Lai等人[Phys.Rev.B75，033314（2007）]研究了调整电荷载流子浓度$n$的Si量子阱结构的表观金属-绝缘体转变（MIT）。他们观察到电导率$σ(T,n)$在费米温度附近的线性温度依赖性，并发现相应的$T \to 0$外推$σ_0(n)$恰好在MIT处表现出急剧弯曲。在这里，重新考虑Lai等人发表的数据，结果表明，这种急剧的弯曲与$σ(T=const.,n)$的特性有关，该特性在整个$T$范围内可清楚地检测到，直到4 K，该工作中的最高测量温度。由于这种特性似乎并不随$T$的增加而平滑，因此它可能表明在有限温度下存在明显的金属和活化导电区域之间的急剧连续相变。这种行为的文献的提示进行了讨论。最后，缩放分析阐明了与以前实验的相似性，并提供了对$d log_{10} σ/ d n (n)$中发现的特性和尖峰形状的理解。
英文摘要：
In a recent experiment, Lai et al. [Phys. Rev. B 75, 033314 (2007)] studied the apparent metal-insulator transition (MIT) of a Si quantum well structure tuning the charge carrier concentration $n$. They observed linear temperature dependences of the conductivity $σ(T,n)$ around the Fermi temperature and found that the corresponding $T \to 0$ extrapolation $σ_0(n)$ exhibits a sharp bend just at the MIT. Here, reconsidering the data published by Lai et al., 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 that work. Since this peculiarity seems not to be smoothed out with increasing $T$ 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 the literature 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 $d log_{10} σ/ d n (n)$.
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