Disorder Induced Phase Transitions of Type-II Weyl Semimetal

Weyl semimetals (WSM) have quickly gained popularity since their discovery and they are now the subject of intense theoretical and experimental research. In general, the WSM is categorized as being either type I or type II. The type-I WSM is characterized by broken inversion symmetry, while the type II by broken Lorentz symmetry. Due to this characteristic difference in the Fermi surfaces of the two types, it is necessary to extend our understanding of WSMs to include the different physical properties that having a tilted spectrum offers. In this vein, disorder-induced phase transitions have been well established for type-I WSMs, while the converse is not the case for type-II WSMs. In this work, the authors demonstrate that the type-I WSM with a nonzero tilting term undergoes a quantum phase transition to the type-II WSM in the presence of random on-site electric and magnetic impurity disorder. They show that the Fermi velocity decreases with increasing disorder strength and, therefore, a type-I to type-II transition occurs before the insulating transition. The conclusion is that the type-I WSM with nonzero tilt will always undergo a disorder-induced transition to the type-II WSM phase.