Quantum Multicriticality in Disordered Weyl Semimetal*

Three-dimensional Weyl semimetal such as layered Chern insulator exhibits a rich variety of quantum phase transitions induced by disorders. Based on numerical calculations of localization length, density of states and critical conductance distribution, we first show that a localization-delocalization transition between a Chern insulator (CI) phase and a diffusive metal (DM) phase belongs to an ordinary 3D unitary class. Moreover, a mobility edge and a band edge of CI-DM phase transition is distinct, which means there is a special area of the CI phase in phase diagram with a finite zero-energy density of states (zDOS) sandwiched between the DM phase and the CI phase with zero zDOS. Meanwhile, a localization-delocalization transition between the CI phase with zero zDOS and a renormalized Weyl semimetal (WSM) phase turns out to be a direct phase transition whose critical exponent ν = 0.80 ± 0.01. We interpret these numerical results by a renormalization group analysis on a quantum multicritical phase transition among CI, DM and WSM phases.