ICQM members report "Disorder and Metal-Insulator Transitions in Weyl Semimetals"

DEC . 23 2015
Peking University, Dec. 22, 2015:   A Ph.D. student Chen Chui-Zhenand his advisor Prof. Xie Xincheng of The International Center for Quantum Materials (ICQM), School of Physics, Peking University, published an article in “Physics Review Letter with the title Disorder and Metal-Insulator Transitions in Weyl Semimetals(PRL. 115, 246603). This work was done in collaboration withPro. Song Juntao from Hebei Normal University, Prof. Jiang Hua from Soochow University, Prof. Sun Qing-feng from ICQM, and Prof. Wang Ziqiang from Boston College.

The newly proposed Weyl semimetal (WSM), a time-reversal symmetry breaking topological quantum state of matter, has been observed recently in real materials (TaAs and NbAs) as well as on optical lattices. It is thus timely to study the effects of disorder, localization, and Anderson type of metal-insulator transitions in WSM systems, both for their direct experimental relevance and for their fundamental value in advancing the understanding of the interplay between randomness and topological order.
Chen et al. do so in this work using both numerical and analytical approaches. Because the WSM has novel gapless excitations, i.e. the Weyl nodes in the bulk and Fermi arcs on the surface, they find an unexpectedly rich phase diagram in the presence of disorder [see Fig.(b)] that is highlighted by the WSM to quantum anomalous Hall insulator transition; the WSM to 3D anomalous Hall metal transition; and the normal band insulator to WSM transition. They address the important issue on the stability of the Weyl nodes and Fermi arcs against weak disorder and obtain the complete phase behaviors for all disorder strengths by calculating the localization length and the Hall conductivity. They propose that the novel disorder-induced phase transitions can be realized on photonic lattices.

(a)       The phase diagram of the clean Weylsemimetal Hamiltonian on the plane.
(b)       The disordered Weyl semimetalphase diagram on the plane. The symbols guided by the solid lines are obtainedfrom the localization length. The bluedashed lines are the phase boundariesdetermined using theSCBA.

The work was supported by National Basic Research Programs of China, National Natural Science Foundation of China, and CollaborativeInnovation Center of Quantum Matter, China.

Edited by: Zhang Jiang
Source: School of Physics