Topological nodal semimetals
Topological nodal semimetals
复制标题
DOI：
10.1103/physrevb.84.235126
复制
发表时间：
2011-12-20
影响因子：
3.7
通讯作者：
Balents, Leon
中科院分区：
文献类型：
--
作者：
Burkov, A. A.;Hook, M. D.;Balents, Leon
我们研究了三维动量空间中非简并导带和价带接触到点(“Weyl半金属”)或线(“线-节点半金属”)的“节点-半金属”相。我们讨论了通过扰动正常绝缘体(NI)和拓扑绝缘体(TI)之间的临界点，打破时间反转(TR)或反转对称性来获得这种状态的一般方法。我们给出了具有破坏的tr对称性的NiTI超晶格结构中这两种态的显式模型实现。Weyl和线节半金属都具有拓扑保护表面态的特征，尽管在线节的情况下，必须施加一些额外的对称性来保持这种拓扑保护。在Weyl半金属的情况下，边态具有“费米弧”的形式：它们是手性无间隙边态，存在于动量空间的有限区域中，由主体Weyl节点的动量-空间分离决定。边态的手征特性导致了有限的霍尔电导。相反，线节点半金属的边缘状态是“平带”：这些状态在二维边缘布里渊区的子集中近似为无色散的，由线节点在边缘平面上的投影给出。我们讨论了节点半金属的异常输运性质，特别是指出了Weyl半金属的DC和光学电导的量子临界标度，以及在线-节点情况下与石墨烯的电导的相似之处。
We present a study of "nodal-semimetal" phases in which nondegenerate conduction and valence bands touch at points (the "Weyl semimetal") or lines (the "line-node semimetal") in three-dimensional momentum space. We discuss a general approach to such states by perturbation of the critical point between a normal insulator (NI) and a topological insulator (TI), breaking either time-reversal (TR) or inversion symmetry. We give an explicit model realization of both types of states in a NI-TI superlattice structure with broken TR symmetry. Both the Weyl and the line-node semimetals are characterized by topologically protected surface states, although in the line-node case, some additional symmetries must be imposed to retain this topological protection. The edge states have the form of "Fermi arcs" in the case of the Weyl semimetal: these are chiral gapless edge states, which exist in a finite region in momentum space, determined by the momentum-space separation of the bulk Weyl nodes. The chiral character of the edge states leads to a finite Hall conductivity. In contrast, the edge states of the line-node semimetal are "flat bands": these states are approximately dispersionless in a subset of the two-dimensional edge Brillouin zone, given by the projection of the line node onto the plane of the edge. We discuss unusual transport properties of the nodal semimetals and, in particular, point out quantum critical-like scaling of the dc and optical conductivities of the Weyl semimetal and similarities to the conductivity of graphene in the line-node case.