Non-Hermitian physical aspects in disordered Weyl/Dirac semimetals*

Recently, the platform of non-Hermitian physics is extended to many-body or disordered systems where quasiparticles possess a finite lifetime. The realization of non-Hermitian topological defects in equilibrium systems attracts great interests because non-Hermiticitian nature makes topological classification very rich. For example, non-Hermitian perturbations in Weyl Hamiltonian lead to the realization of Weyl exceptional rings and flat bands.

Here, we show the non-Hermitian physics in disordered Weyl semimetals. In this presentation, we propose a general scheme for the generation of disorder-induced Weyl exceptional rings, a spectral collapse of Landau levels. Our scheme for a generation Weyl exceptional ring is applicable to almost all Weyl materials. Thus, Weyl exceptional rings in disordered Weyl semimetals are detectable by using photoemission or quasiparticle interference experiments.
In addition, we propose that a new type of non-Hermitian effects in Weyl semimetals, the spectral collapse of Landau levels. We show that non-Hermitian perturbation leads to the collapse of Landau quantization which corresponds to non-Hermitian topological phase transition.