title: Disorder and Metal-Insulator Transitions in Weyl Semimetals.
abstract: The Weyl semimetal (WSM) is a newly proposed quantum state of matter. It has Weyl nodes in bulk excitations and Fermi arc surface states. We study the effects of disorder and localization in WSMs and find three novel 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 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 novel phase transitions can be realized on a photonic lattice.
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
authors.forename: Chui-Zhen
authors.initials: CZ
authors.lastname: Chen
authors.affiliation: Department of Physics, Hebei Normal University, Hebei 050024, China.
authors.forename: Juntao
authors.initials: J
authors.lastname: Song
authors.affiliation: College of Physics, Optoelectronics and Energy, Soochow University, Suzhou 215006, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Jiang
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
authors.forename: Qing-feng
authors.initials: QF
authors.lastname: Sun
authors.affiliation: Department of Physics, Boston College, Chestnut Hill, Massachusetts 02167, USA.
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
authors.forename: X C
authors.initials: XC
authors.lastname: Xie