极端条件下5d过渡金属化合物中的拓扑量子态研究

Topological quantum state means the new electronic state induced by the quantum effects that are related to some topological properties of the materials. The most important feature of these electronic states is the invariance under local deformation, in another word, these states are insensitive to the perturbation of the environment. This feature makes the topological quantum states have great application potential in high-speed-low-energy-cost spintronic devices and fault-tolerant quantum computers. Searching for new topological matter states becomes the focus of the condensed matter physics research. Since 5d electrons have strong spin-orbit coupling, the 5d-based transition-metal compounds have been theoretically predicted having abundant topological quantum states, most of which have not been verified by experiments yet. Therefore, performing experimental research on the topological quantum states is very important. We plan to study the possible topological quantum states in the 5d-based transition-metal compounds by applying high magnetic field and ultra-high pressure, investigate the physical phenomena like Majorana fermion, magnetic monopole which have great influence to the fundamental physics, and provide experimental supports to the research on the topological quantum states.

拓扑量子态是指材料中与某些拓扑性质相联系的量子效应所导致的新的电子态。这些电子态一个最重要的性质是局部形变下的不变性，即对于环境微扰的不敏感性，这个特性使得拓扑量子态在未来的高速低能耗自旋电子器件和容错量子计算机中有广阔的应用前景，寻找新的拓扑物质形态也成为了近年来凝聚态物理的研究热点。由于5d电子有着强烈的自旋轨道耦合，5d过渡金属化合物被理论预言存在丰富的拓扑量子态。这些拓扑量子态许多尚未得到实验证实，需要开展实验研究特别是输运性质研究加以验证。我们拟利用稳态强磁场实验装置及其综合极端实验条件，通过外加强磁场和超高压来研究体系中可能存在的拓扑量子态，探索Majorana费米子、磁单极子等对基础物理影响深远的物理现象，为拓扑量子态研究提供实验基础。

拓扑量子态在未来的高速低能耗自旋电子器件和容错量子计算机中有广阔的应用前景。寻找新的拓扑物质形态也成为了近年来凝聚态物理的研究热点。由于5d电子有着强烈的自旋轨道耦合，5d过渡金属化合物被理论预言存在丰富的拓扑量子态。这些拓扑量子态许多尚未得到实验证实，需要开展实验研究特别是输运性质研究加以验证。在本项目中，我们利用稳态强磁场实验装置，开展了NdSb/DySb等材料的磁结构转变、TaP/MoTe2/低维Dirac半金属/新型node-arc半金属等体系中的量子输运行为、铱氧化物的磁相变临界行为、关联电子体系量子激发等研究，从实验上发现了磁性拓扑半金属材料，观察到拓扑半金属中的平面霍尔效应、一维拓扑半金属中的非平庸贝里相等物理现象，为深入理解拓扑非平庸体系提供了新的证据。项目共发表SCI论文23篇，包括7篇Phys. Rev. B和2篇Appl. Phys. Lett.。