Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators
Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators
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DOI：
10.1103/physrevb.98.214203
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发表时间：
2018-12-19
影响因子：
3.7
通讯作者：
Yacoby, A.
中科院分区：
文献类型：
--
作者：
Nandi, D.;Skinner, B.;Yacoby, A.
在超薄拓扑绝缘子（TI）膜中，在Ti表面状态下打开杂交间隙，并且当化学电位在杂交间隙内时，预计该系统将成为琐碎的绝缘体或量子自旋霍尔绝缘子。但是，我们在这里表明，这些绝缘状态被大型且远程相关的疾病潜力的存在破坏，从而将预期的绝缘子转化为金属。我们在超薄双门控拓扑绝缘子膜中执行传输测量，这是温度，栅极电压和磁场的函数，并且我们观察到金属样的非量化电导率，在低磁场上表现出弱的抗静电性尖端，并在大型领域具有不含有线性磁力磁性的方式。我们通过考虑由电荷杂质引起的电子和孔型水坑的无序网络来解释这些结果。从理论上讲，我们认为这种疾病可以产生绝缘体到金属的过渡，这是无序强度的函数，并且我们在带隙和观察绝缘状态所需的杂质浓度上得出了条件。我们还使用数值模拟和理论缩放参数来解释局部电导率的强空间波动的线性磁倍率。
In an ultrathin topological insulator (TI) film, a hybridization gap opens in the TI surface states, and the system is expected to become either a trivial insulator or a quantum spin Hall insulator when the chemical potential is within the hybridization gap. Here we show, however, that these insulating states are destroyed by the presence of a large and long-range-correlated disorder potential, which converts the expected insulator into a metal. We perform transport measurements in ultrathin dual-gated topological insulator films as a function of temperature, gate voltage, and magnetic field, and we observe a metalliclike nonquantized conductivity, which exhibits a weak antilocalizationlike cusp at low magnetic fields and gives way to a nonsaturating linear magnetoresistance at large fields. We explain these results by considering the disordered network of electron- and hole-type puddles induced by charged impurities. We argue theoretically that such disorder can produce an insulator-to-metal transition as a function of increasing disorder strength, and we derive a condition on the band gap and the impurity concentration necessary to observe the insulating state. We also explain the linear magnetoresistance in terms of strong spatial fluctuations of the local conductivity using both numerical simulations and a theoretical scaling argument.