Conductivity of two-dimensional narrow gap semiconductors subjected to strong Coulomb disorder
Conductivity of two-dimensional narrow gap semiconductors subjected to strong Coulomb disorder
复制标题
DOI：
10.1103/physrevb.105.054206
复制
发表时间：
2021-11
影响因子：
3.7
通讯作者：
Yi Huang;Yanjun He;B. Skinner;B. Shklovskii
中科院分区：
文献类型：
--
作者：
Yi Huang;Yanjun He;B. Skinner;B. Shklovskii
在理想的无无序情况下，二维带隙绝缘体的电导率激活能等于带隙的一半。但输运实验在低温下通常表现出很小的活化能，并且该活化能与介电常数之间的关系尚不清楚。在这里，我们考虑的温度依赖的二维绝缘体上含有库仑杂质的基板，与随机电位振幅Γ π π。我们表明，一般表现出三个政权的导电性，只有最高温度制度表现出的活化能，反映了带隙。在较低的温度下，传导通过激活跳跃或Efros-Shklovskii可变范围跳跃在由无序产生的电子和空穴水坑之间进行。我们发现，与这些过程相关的激活能和特征温度急剧崩溃附近的临界杂质浓度。较大的浓度导致指数小的活化能和指数长的局域化长度，这在介观样品中可以表现为无序诱导的绝缘体到金属的转变。我们也到达一个类似的陡峭的无序驱动的绝缘体-金属过渡的三维拓扑绝缘体的薄膜具有大的介电常数，膜内的库仑杂质创建一个大的无序电位由于限制其电场内的膜。
In the ideal disorder-free situation, a two-dimensional band-gap insulator has an activation energy for conductivity equal to half the band gap ∆. But transport experiments usually exhibit a much smaller activation energy at low temperature, and the relation between this activation energy and ∆ is unclear. Here we consider the temperature-dependent conductivity of a two-dimensional insulator on a substrate containing Coulomb impurities, with random potential amplitude Γ ≫ ∆. We show that the conductivity generically exhibits three regimes of conductivity, and only the highest-temperature regime exhibits an activation energy that reflects the band gap. At lower temperatures, the conduction proceeds through activated hopping or Efros-Shklovskii variable-range hopping between electron and hole puddles created by the disorder. We show that the activation energy and characteristic temperature associated with these processes steeply collapse near a critical impurity concentration. Larger concentrations lead to an exponentially small activation energy and exponentially long localization length, which in mesoscopic samples can appear as a disorder-induced insulator-to-metal transition. We also arrive at a similar steep disorder driven insulator-metal transition in thin films of three-dimensional topological insulators with large dielectric constant, for which Coulomb impurities inside the film create a large disorder potential due to confinement of their electric field inside the film.