Artificial event horizons in Weyl semimetal heterostructures

Heterostructures comprising type-I and type-II Weyl semimetals give rise to effective spacetimes featuring black or white hole event horizons [1] with the prospect of electronic analogs of Hawking radiation and gravitational lensing, among others. We investigate transport in this system using a minimal model for a Weyl semimetal with a position-dependent tilt of the Weyl cone. We provide an exact solution to the scattering problem at normal incidence for energies close to the Weyl node, both for a fast and a slow varying tilt profile relative to the Fermi wavelength. In the latter case, we find analogous Hawking radiation in two transport channels which cancel one another in equilibrium. We show that one can favor the contribution of one channel using a non-equilibrium state, either by irradiating the type-II region or by injecting a spin-polarized current. This in turn gives rise to a characteristic peak in the two-terminal differential conductance which can serve as an experimental indicator of the artificial event horizon.

[1] G. E. Volovik, Jetp Lett. 104,645 (2016).