拓扑绝缘体量子点接触中的量子输运研究

三维拓扑绝缘体独特的表面态具有许多新奇的物理特性，如线性狄拉克色散关系、自旋-动量方向锁定，成为研制拓扑量子器件和自旋电子器件的重要体系。理论研究表明，在拓扑绝缘体一维体系中，量子尺寸效应导致二维表面态会形成离散的一维子带。本项目拟采用刻蚀的方法在三维拓扑绝缘体中构建量子点接触，通过低温输运测量研究量子点接触中拓扑表面态的电导量子化，寻找拓扑表面态形成离散化一维子带和一维螺旋态的直接证据；进一步，研究量子点接触结构中第一个量子电导平台附近的分数倍电导异常结构，通过研究分数倍电导异常结构对不同方向磁场的响应，以及随温度、栅压、偏压等条件的演化，理解自旋轨道耦合作用对分数倍电导异常结构的影响，为进一步研制基于拓扑绝缘体的拓扑量子器件和自旋电子器件探索新原理和新方法。

The unique surface states make topological insulators promising for developing topological quantum devices and spintronic devices. Theoretical studies show in one-dimensional system of topological insulator, two-dimensional topological surface states form discrete one-dimensional subbands due to quantum size effect. In this project, new etching method is proposed to construct the quantum point contact in three-dimensional topological insulators. Through the low-temperature transport measurements, we will study the conductance quantization of the topological surface state in the quantum point contact to find the direct evidence of the discrete one-dimensional subbands and the helical state. Furthermore, we plan to study the fractionally quantized conductance plateau near the first conductance plateau. Through the response of the fractional quantized conductance plateau to magnetic field in different directions, and the evolution with temperature, gate voltage and bias voltage, to understand the effect of spin-orbit coupling on the fractional quantized conductance plateau. These studies will open up possibilities of achieving topological quantum devices and spintronic devices based on the topological insulator.