二维六角晶体材料中能谷极化电流的产生、调控和测量

The broad investigation of two-dimensional hexagonal lattice materials provides a new platform for new quantum phenomena and electronic manipulation in multi degrees of freedom. Two-dimensional materials, such as graphene and two-dimensional transition metal dichalcogenides, have special valley indexes in the band structure. They are important objects for the generation, modulation, storage and read of valley resolved electronic states. The project concerns the theoretical investigation of new topological protected states in two-dimensional hexagonal lattice materials, for the construction of valley valves to host valley polarization current which is robust against disorder and can survive in a long distance; taking advantage of the absence of backscattering in topological quantum states, manipulate the magnitude and polarization of valley polarized current through quantum interference with electric field and magnetic field; propose new approaches to measure the magnitude and valley polarization of valley polarized current; provide theoretical explanation for the non-local measurement of valley Hall effect in bilayer graphene; study the experimental accessible quantum valley Hall effect and investigate its electronic transport properties. The investigations focus on the generation, manipulation and measurement of valley polarized current, can not only enrich the manipulation manners of valley polarized current, reveal the mechanisms of valley transport, but also will promote the application of valleytronics.

凝聚态物理中二维六角晶体材料的广泛研究为新奇量子效应的发现和电子的多自由度操控提供新的平台。以石墨烯和二维过渡金属硫化物等为代表的二维六角晶体材料具有特别的“谷”能带结构，是研究谷极化电子态产生、调制、存储和读取的重要对象。本项目拟理论研究新型二维六角晶体材料中能谷极化的拓扑保护电子态，用于构造谷阀门以产生可对抗电子无序、可长程保持强度的谷极化电流；利用拓扑保护的量子态背散射较弱的优点，通过量子干涉用电磁调控实现可控大小和极化率的谷极化流；提出新型电学测量方案，以探测谷极化流的大小和极化率；解释实验上双层石墨烯中能谷电流输运的非局域测量结果；探究实验上实现量子谷霍尔效应的可能方案并研究其输运性质。这些问题的研究着眼于二维六角晶体材料中能谷极化流的产生、调控和测量，不仅可实现能谷极化电流的电学操控、深入揭示能谷极化电子的输运机制，也将推动谷电子学的应用。

以石墨烯为代表的二维蜂窝结构晶体具有独特的能带结构和电学性质。这样的材料通常由两套格子嵌套而成。在第一布里渊区能带有两个不等价的“谷”或“能谷”。能谷电子学致力于研究谷自由度电子量子态的操控，希望应用于量子信息的操控、编码、存储和读取。本项目着眼于近年来类石墨烯二维六角晶体电子材料，通过调节和控制能谷指标研究谷电子学以及其它拓扑态的输运性质。主要研究各种能谷极化的拓扑态的产生、调控和电子输运性质；人造石墨烯中构建其它新奇的拓扑量子态，且通过电子输运来证明这些态的存在；在基于石墨烯的模型中，通过改变无序的分布来实现研究新型拓扑态并寄希望其在于宏观电路的实现。依托本项目支持，我们在拓扑界面态上做出一系列工作，包括拓扑界面态的调控、石墨烯和人造石墨烯体系中其它新奇的量子态，也解释了三维霍尔效应中的实验结果。项目组成员以通讯/第一作者身份发表论文12篇，其中包括Physical Review Letters，Physical Review B 等高影响力权威期刊。这些结果不仅实现了能谷极化电流的电学操控、深入揭示拓扑保护电子态的输运机制，构建了更容易实现新型拓扑态的平台，也将推动谷电子学的应用。