Disorder-induced phase transitions of type-II Weyl semimetals

Weyl semimetals are a newly discovered class of materials that host relativistic massless Weyl fermions as their low-energy bulk excitations. Among this class of materials, there exist two types of semimetals that are of particular interest: type-I Weyl semimetals, which have broken inversion or time-reversal symmetry, and type-II Weyl semimetals, which additionally break Lorentz invariance, hosting tilted Weyl cone. In this work, we use the Born approximation to demonstrate that the type-I Weyl semimetals undergo a quantum phase transition to type-II Weyl semimetals in the presence of the finite Anderson disorder when non-zero tilt of Weyl cone exists. The phase transition occurs when the disorder renormalizes the topological mass, thereby reducing the Fermi velocity near the Weyl cone below the tilt of the cone. We also confirm the presence of the disorder-induced phase transition in Weyl semimetals by using exact diagonalization of a three-dimensional tight-binding model to calculate the resultant phase diagram of the
type-I Weyl semimetal.

Reference : M. J. Park, B. Basa, and M. J. Gilbert Phys. Rev. B 95, 094201 (2017)