标题： 无序与外尔半金属中的金属-绝缘体转变 显示英文标题

标题： Disorder and metal-insulator transitions in Weyl semimetals

摘要： 外尔半金属（WSM）是一种新提出的物质量子态。 它在体激发中具有外尔节点，在费米弧表面态中也存在。 我们研究了WSMs中的无序和局域化效应，并发现了三种奇异的相变。 (I) 接近布里渊区边界的两个外尔节点可以通过无序散射成对湮灭，导致拓扑非平凡能隙的打开，并从WSM转变为三维（3D）量子反常霍尔态。 (II) 当两个外尔节点在动量空间中分离良好时，产生的体扩展态可以导致从WSM直接转变为三维扩散反常霍尔金属。 (III) 当绝缘能隙随着无序增加而关闭时，两个外尔节点可以在区域中心附近出现，从而实现从正常带绝缘体到WSM的直接转变。 我们通过数值计算局域化长度和霍尔电导来确定相图，并提出这些奇异的相变可以在光子晶格上实现。 显示英文摘要

摘要： The Weyl semimetal (WSM) is a newly proposed quantum state of matter. It has Weyl nodes in bulk excitations and Fermi arcs surface states. We study the effects of disorder and localization in WSMs and find three exotic phase transitions. (I) Two Weyl nodes near the Brillouin zone boundary can be annihilated pairwise by disorder scattering, resulting in the opening of a topologically nontrivial gap and a transition from a WSM to a three-dimensional (3D) quantum anomalous Hall state. (II) When the two Weyl nodes are well separated in momentum space, the emergent bulk extended states can give rise to a direct transition from a WSM to a 3D diffusive anomalous Hall metal. (III) Two Weyl nodes can emerge near the zone center when an insulating gap closes with increasing disorder, enabling a direct transition from a normal band insulator to a WSM. We determine the phase diagram by numerically computing the localization length and the Hall conductivity, and propose that the exotic phase transitions can be realized on a photonic lattice.