探索在二维空穴-超导结中的奇异拓扑粒子

The discovery of the Majorana Fermion (MF) is one of the most important topics in physics. Due to the recent development of the topological insulator (TI) and nanowire, with more and more theoretical evidences present; the searching for the Majorana Fermion in solid matters become a hot spot in condensed matter physics. In the past two years, some experimental evidences were reported by several research groups; all the experiments were carried out on the materials of nanowire (NW) and s-wave superconductor (SC) proximity to each other. However, due to the limit of the device structure and the nanowire materials, present works do not show the definite evidence for the Majorana elementary excitation. Based on the new theoretical proposal, we would like to prepare Quantum point contact (QPC) on the p-type GaAs (two-dimensional hole)- superconductor junction device, study the Majorana elementary excitation by the quantum transport measurements. Compare to the nanowire-superconductor structure, the new device has better tolerance to the imperfect temperature and more impurities. It is much easier to carry out the experiments on the Majorana fermions. We would like to clarify the evidence for the Majorana elementary excitation in our plan, and support the development for the topological quantum computation (TQC).

探索马约拉纳费米子一直以来是物理学领域的重要问题之一。近年来，随着拓扑绝缘体和纳米线研究的发展，在固体物质中探索马约拉纳型元激发成为凝聚态物理研究的热点，支持马约拉纳型元激发存在的理论工作层出不穷。两年来，国际上先后有多个小组报道了马约拉纳型元激发存在的可能证据，这些实验均基于纳米线与s波超导体近邻的材料体系。然而，由于器件结构和纳米线材料本身的限制，现有的实验尚不能作为马约拉纳型元激发存在的确切证据。本项目借鉴了相关的理论研究结果，拟制作具有量子点接触结构的p型GaAs空穴气-超导结器件，通过测量低温输运，探索马约拉纳型元激发的性质。该器件结构相对于纳米线-超导结构而言，对温度、杂质等非理想条件有更高的容忍性，且可供研究的输运性质更为丰富，因而更易于在实验上实现对马约拉纳型元激发的观测。通过本项目的开展，我们希望给出马约拉纳型元激发存在与否的确凿证据，并为拓扑量子计算的开展提供平台。

本项目基于在半导体二维电子（或空穴）系统中发展半导体-超导结输运研究，以探索如马约拉纳费米子等拓扑奇异电子态。我们首先发展了二维空穴系统的电子相研究，包括空穴系统的Wigner晶格（固体）的输运性质和特征长度，在微波辐照下的磁场B-周期的边缘等离子态振荡等。同时以奇异拓扑态为导向，研究了拓扑绝缘体和外尔费米子的输运研究，并在奇异电子相方面有所发现。这些发现对于潜在的马约拉纳费米子研究提供了基础。