拓扑半金属材料合成探索及外场调控研究

Recent discovered three-dimensional (3D) Dirac and Weyl semimetals represent a new state of topological quantum matter. This material can be viewed as a three- dimensional (3D) analogue of graphene and has linear energy dispersion in bulk, leading to a range of exotic transport properties, such as ultra-high carrier mobility and very large non-saturating magnetoresistance (MR). Many materials were predicted to be Dirac/Weyl semimetals, only a few of them were confirmed yet. Discovering new Dirac/Weyl semimetals with novel properties has become an important front in condensed matter and material sciences. In this project, we attempt to synthesis several newly predicted topological semimetals, including SrSn2As2, CuMnAs, MoP2, WP2, ZrTe, WC et al. We will firstly investigate the quantum transport properties of the obtained crystals at high magnetic fields and low temperatures. Then the transport behavior of these materials will be tuned by external high pressures or electric fields. The detailed electronic band structure of the obtained materials will also be investigated with ab initio calculation. Through these studies, we hope to obtain experimental evidences of several predicted topological semimetals and to explore the relations between the transport properties and electronic band structures. The proposed work is expected to shed new light on the future design of new topological semimetals and promoting their practical applications.

拓扑半金属是一类全新的拓扑电子态，可以看作“三维石墨烯”，可用于实现极低能耗的电子输运，特别是对室温低能耗电子学器件的应用具有重要价值。探索新的Dirac/Weyl半金属，并研究可能出现的各种量子现象，是目前凝聚态物理研究领域中的热门课题。理论计算结果预言了很多体系可能为Dirac/Weyl半金属材料，但只有很少一部分被证实。本项目中我们将基于理论计算结果，开展几种拓扑半金属材料（如SrSn2As2, CuMnAs, MoP2, WP2, ZrTe, WC等）合成研究，并结合强磁场、极低温实验条件，以及高压、电场调控和微纳加工技术等，对材料的电输运性能开展详细测量，探索可能出现的奇异量子行为。同时结合能带计算，对其电子结构进行深入研究。项目将力争合成出3-4种具有高迁移率、大磁电阻的新拓扑半金属材料，并揭示这些材料电子能带结构和输运性能之间的关系，为进一步推动拓扑半金属材料研究做出贡献。

拓扑半金属是一类全新的拓扑电子态，可用于实现极低能耗的电子输运，特别是对室温低能耗电子学器件的应用具有重要价值。探索新的拓扑量子材料，并研究可能出现的各种量子现象，是目前凝聚态物理研究领域中的热门课题。项目执行期间，集中开展了多种新型拓扑量子材料的合成探索和性能研究工作，以及相关器件的构筑与性能调控，取得了一系列进展，包括：（1）发现新的三重简并拓扑半金属——层状PtBi2；（2）证实了灰砷（Gray arsenic）中存在狄拉克拓扑态；（3）在层状化合物TaNiTe5中观察到具有三维特征的非平庸拓扑能带；（4）通过对Nb3SiTe6纳米片强磁场下的输运特性研究，证实其为节线（Nodal-line）半金属；（5）在狄拉克半金属ZrTe5中发现强磁场诱导拓扑量子相变；（6）在狄拉克半金属Cd3As2纳米片中，通过非局域电输运测量的方法观察到表面态费米弧，给出一种探测拓扑半金属费米弧表面态的新方法；给出了三维拓扑半金属中存在平面霍尔效应的直接证据等；（7）在反铁磁拓扑绝缘体MnBi2Te4中发现π/2周期的平面霍尔效应。相关研究工作发表论文11篇，包括Nature Communications 1篇， Nano Letters 1篇，Science Bulletin 1篇，Phys. Review B 6 篇， Chinese Physics Letters 2篇。