Terahertz cyclotron emission from two-dimensional Dirac fermions

TL;DR

This paper reports the experimental observation of tunable terahertz cyclotron emission from gapped Dirac fermions in HgTe quantum wells, advancing the development of tunable Landau lasers for terahertz applications.

Contribution

It demonstrates Landau emission from Dirac fermions in HgTe quantum wells with a tunable emission, addressing previous challenges in realizing Landau lasers with graphene-like materials.

Findings

Observation of tunable terahertz emission in HgTe quantum wells

Emission controllable by magnetic field and carrier concentration

Progress towards terahertz Landau laser development

Abstract

Since the emergence of graphene, we have seen several proposals for the realization of Landau lasers tunable over the terahertz frequency range. The hope was that the non-equidistance of the Landau levels from Dirac fermions would suppress the harmful non-radiative Auger recombination. Unfortunately, even with this non-equidistance an unfavorable non-radiative process persists in Landau-quantized graphene, and so far no cyclotron emission from Dirac fermions has been reported. One way to eliminate this last non-radiative process is to sufficiently modify the dispersion of the Landau levels by opening a small gap in the linear band structure. A proven example of such gapped graphene-like materials are HgTe quantum wells close to the topological phase transition. In this work, we experimentally demonstrate Landau emission from Dirac fermions in such HgTe quantum wells, where the emission is tunable by both the magnetic field and the carrier concentration. Consequently, these results represent an advance in the realization of terahertz Landau lasers tunable by magnetic field and gate-voltage.