Special CPM Seminar

Quantum Magnetoconductivity in Topological Semimetals

Shun-Qing Shen

Department of Physics
University of Hong Kong

Weyl semimetals are three-dimensional topological states of matter, in a sense that they host paired monopole and anti-monopole of Berry curvature in momentum space, leading to the chiral anomaly. The chiral anomaly has long been believed to give a positive magnetoconductivity in strong and parallel fields. However, several recent experiments on both Weyl and Dirac topological semimetals show a negative magnetoconductivivity at high fields and a signature of weak antilocalization in a weak field. Here, we study the magnetoconductivity of Weyl and Dirac semimetals in the diffusive regime. In a weak field we demonstrate that the quantum interference effect gives rise a cusp-like positive magnetoconductivity as a signature of weak anti-localiztion. In a strong magnetic field applied along the direction that connects two Weyl nodes, we find that the conductivity along the field direction is determined by the Fermi velocity. We identify three cases in which the high-field magnetoresistance is positive. Our findings show that the high-field negative magnetoresistivity may not be a compelling signature of the chiral anomaly and will be helpful for interpreting the inconsistency in the recent experiments and earlier theories.

References:
1. Weak antilocalization and localization in disordered and interacting Weyl semimetals, Hai-Zhou Lu and Shun-Qing Shen, Physical Review B 92, 035203 (2015).
2. High-field magnetoconductivity of topological semimetals with short-range potential, Hai-Zhou Lu, Song-Bo Zhang, Shun-Qing Shen, Physical Review B 92, 045203 (2015).