# Artificial event horizons in Weyl semimetal heterostructures and their non-equilibrium signatures

### Submission summary

 As Contributors: Christophe De Beule · Solofo Groenendijk Arxiv Link: https://arxiv.org/abs/2106.14595v3 (pdf) Date accepted: 2021-09-29 Date submitted: 2021-09-13 11:52 Submitted by: De Beule, Christophe Submitted to: SciPost Physics Academic field: Physics Specialties: Condensed Matter Physics - Theory Approach: Theoretical

### Abstract

We investigate transport in type-I/type-II Weyl semimetal heterostructures that realize effective black- or white-hole event horizons. We provide an exact solution to the scattering problem at normal incidence and low energies, both for a sharp and a slowly-varying Weyl cone tilt profile. In the latter case, we find two channels with transmission amplitudes analogue to those of Hawking radiation. Whereas the Hawking-like signatures of these two channels cancel in equilibrium, we demonstrate that one can favor the contribution of either channel using a non-equilibrium state, either by irradiating the type-II region or by coupling it to a magnetic lead. This in turn gives rise to a peak in the two-terminal differential conductance which can serve as an experimental indicator of the artificial event horizon.

Published as SciPost Phys. 11, 095 (2021)

Dear Editor,

We would like to resubmit our manuscript entitled "Artificial event horizons in Weyl semimetal heterostructures and their non-equilibrium signatures'' to SciPost Physics.

We thank both Referees for carefully reading our manuscript and for their helpful comments which allowed us to improve the manuscript.
We believe that we have addressed all comments of both Referees an have updated our manuscript accordingly. We hope that it is now ready for publication in SciPost Physics.

Sincerely,

Christophe De Beule, Solofo Groenendijk, Tobias Meng, and Thomas L. Schmidt

### List of changes

1. We have added a derivation of the effective metric with the tetrad formalism in the introduction. Details of the calculation and a small introduction to tetrads can be found in the new Appendix A.
2. We realized that we made an error in deriving the steady state distribution function in Sec. 4.1. In the steady state $\partial n / \partial t$ vanishes (see new Eq. 75) and the term involving $\dot{\bm r}$ is neglected in the long wavelength limit ($\Omega \ll E_F c/v_F$) while the term involving $\dot{\bm k}$ contains the AC response. In the DC limit, one can also neglect the latter term leading to Eq. 78. However, we stress that this does not affect any of our results. In particular, the non-equilibrium distribution function remains the same, but it is now correctly identified with the second-order DC response.
3. Several minor changes which are detailed in our reply to the Referees. In particular, we have modified the discussion on the semiclassical trajectories and the black hole analogy in the introduction, as well as an additional paragraph in the conclusion concerning experimental implications.

### Submission & Refereeing History

#### Published as SciPost Phys. 11, 095 (2021)

Resubmission 2106.14595v3 on 13 September 2021
Submission 2106.14595v1 on 6 July 2021

## Reports on this Submission

### Report

The authors have given sufficient response to all concerns in my original referee report. I am convinced that their article meets all acceptance criteria for SciPost physics and I recommend publication. (Please see my first report for a more thorough analysis of the scientific content of the article.)

• validity: high
• significance: high
• originality: high
• clarity: high
• formatting: excellent
• grammar: perfect