title: Chern semimetal and the quantized anomalous Hall effect in HgCr2Se4.
abstract: In 3D momentum space, a topological phase boundary separating the Chern insulating layers from normal insulating layers may exist, where the gap must be closed, resulting in a "Chern semimetal" state with topologically unavoidable band crossings at the Fermi level. This state is a condensed-matter realization of Weyl fermions in (3+1)D, and should exhibit remarkable features, such as magnetic monopoles and Fermi arcs. Here we predict, based on first principles calculations, that such a novel quantum state can be realized in a known ferromagnetic compound HgCr2Se4, with a single pair of Weyl fermions separated in momentum space. The quantum Hall effect without an external magnetic field can be achieved in its quantum-well structure.
authors: Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors: Gang
authors: G
authors: Xu
authors: Hongming
authors: H
authors: Weng
authors: Zhijun
authors: Z
authors: Wang
authors: Xi
authors: X
authors: Dai
authors: Zhong
authors: Z
authors: Fang