Faculty of Science, Department of Physics, Istanbul University, Vezneciler, Istanbul 34134, Turkey.
Department of Physics, Science and Letters Faculty, Mimar Sinan Fine Arts University, Sisli, Istanbul 34380, Turkey.
Nat Commun. 2017 Jan 10;8:14082. doi: 10.1038/ncomms14082.
Since the experimental realization of the integer quantum Hall effect in a two-dimensional electron system, the interrelation between the conductance quantization and the topological properties of the system has been investigated. Assuming that the two-dimensional electron system is described by a Bloch Hamiltonian, system is insulating in the bulk of sample throughout the quantum Hall plateau due to a magnetic field induced energy gap. Meanwhile, the system is conducting at the edges resembling a 2+1 dimensional topological insulator without time-reversal symmetry. Here, by our magneto-transport measurements performed on GaAs/AlGaAs high purity Hall bars with two inner contacts we show that incompressible strips formed at the edges result in Hall quantization, even if the bulk is compressible. Consequently, the relationship between the quantum Hall effect and topological bulk insulator breaks for specific field intervals within the plateaus. The measurement of conducting bulk, strongly challenges all existing single-particle theories.
自从在二维电子系统中实验实现整数量子霍尔效应以来，人们一直在研究电导量子化与系统拓扑性质之间的关系。假设二维电子系统由布洛赫哈密顿量描述，由于磁场诱导的能隙，系统在整个量子霍尔平台中在样品的体部分都是绝缘的。同时，系统在类似于没有时间反演对称性的 2+1 维拓扑绝缘体的边缘处是导电的。在这里，我们通过在具有两个内接触的 GaAs/AlGaAs 高纯霍尔条上进行的磁输运测量表明，即使在体部分是可压缩的情况下，在边缘形成的不可压缩条带也会导致霍尔量子化。因此，在平台内的特定磁场区间内，量子霍尔效应和拓扑体绝缘之间的关系被打破。对导电体的测量强烈挑战了所有现有的单粒子理论。
