Probing the chiral anomaly with nonlocal transport in three dimensional topological semimetals
S. A. Parameswaran, T. Grover, D. A. Abanin, D. A. Pesin, A. Vishwanath
备注：
10 pages, 5 figures; substantial revisions include applications to Dirac semimetals and a treatment of impurity scattering and imbalance relaxation. Version accepted in Phys. Rev. X
Weyl semimetals are three-dimensional crystalline systems where pairs of bands touch at points in momentum space, termed Weyl nodes, that are characterized by a definite topological charge: the chirality. Consequently, they exhibit the Adler-Bell-Jackiw anomaly, which in this condensed matter realization implies that application of parallel electric ($\mathbf{E}$) and magnetic ($\mathbf{B}$) fields pumps electrons between nodes of opposite chirality at a rate proportional to $\mathbf{E}\cdot\mathbf{B}$. We argue that this pumping is measurable via nonlocal transport experiments, in the limit of weak internode scattering. Specifically, we show that as a consequence of the anomaly, applying a local magnetic field parallel to an injected current induces a valley imbalance that diffuses over long distances. A probe magnetic field can then convert this imbalance into a measurable voltage drop far from source and drain. Such nonlocal transport vanishes when the injected current and magnetic field are orthogonal, and therefore serves as a test of the chiral anomaly. We further demonstrate that a similar effect should also characterize Dirac semimetals --- recently reported to have been observed in experiments --- where a pair of Weyl nodes coexisting at a single point in the Brillouin zone are protected by a crystal symmetry. Since the nodes are analogous to valley degrees of freedom in semiconductors, this suggests that valley currents in three dimensional topological semimetals can be controlled using electric fields, which has potential practical `valleytronic' applications.
Nonlocal drag by topological surface magnons in a pyrochlore ferromagnet
准粒子波函数的非平凡拓扑可以以可观测的表面态的形式表现出来。这在电子系统中已经很好地建立起来，狄拉克和外尔半金属将这些拓扑保护实体的奇异性质带到了前面。磁振子--指的是局部自旋的集体激发--提供了另一个领域，其中许多概念可以实现。在这里，我们报告的烧绿石铁磁体，理论上预测主机等拓扑磁振子的磁热测量。结果表明，在Y $_2$ V $_2$ O $_7$单晶样品上沉积金属层的热电势可以用来测量磁振子霍尔效应。此外，拓扑保护的磁振子表面状态的直接表现形式被观察到-通过这些表面自旋电流施加在相邻金属层的传导电子的界面阻力。
Coherent magnetic excitations in a topological Kondo semimetal
Zhejiang University（浙江大学）；ISIS Facility, STFC Rutherford Appleton Laboratory（STFC卢瑟福阿普尔顿实验室ISIS设施）；University of Johannesburg（约翰内斯堡大学）；Tokyo Metropolitan University（东京都立大学）；Indian Institute of Science（印度科学学院）；J-PARC Center（日本质子加速器研究机构中心）；Hiroshima University（广岛大学）；Institute for Advanced Study in Physics, Zhejiang University（浙江大学物理学高等研究院）；Institute of Fundamental and Transdisciplinary Research, Zheji（浙江基础与交叉研究学院）
The flow of local quantum fluids: Conservation laws and vertex corrections from many-body linear-response theory with local self-energy
Institut für Quantenmaterialien und Technologien, Karlsruher Institut für Technologie（量子材料与技术研究所，卡尔斯鲁厄理工学院）；Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie（凝聚态理论研究所，卡尔斯鲁厄理工学院）
Switching of topological phase transition from semiconductor to ideal Weyl states in Cu$_2$SnSe$_3$ family of materials
Guilin University of Technology（桂林理工大学）；Key Laboratory of Low-dimensional Structural Physics and Application, Education Department of Guangxi Zhuang Autonomous Region（广西低维结构物理与应用重点实验室）
