Spectrum Collapse of Disordered Dirac Landau Levels as Topological Non-Hermitian Physics

We investigate disorder effects on Landau levels in Dirac electron systems with the use of a non-Hermitian quasiparticle Hamiltonian formalism. This formalism reveals that spin-dependent scattering rates induce spectrum collapse levels, i.e., disappearance energy gaps between n-th and -n-th under finite external magnetic field. The occurs both weak strong field regimes, thus showing reentrant behavior. Particularly, regime, contrast to naive expectation, increase stabilizes levels. Furthermore, it is revealed associated emergence vortex texture topological winding number complex system.