The discovery of Dirac fermions in a number of 2D and 3D materials boosted the solid-state research in an unprecedented way. Among the many hopes of using their exceptional physical properties, it has been argued that their reduced nonradiative losses would allow graphene to compete with quantum cascade lasers (QCLs) in the race for terahertz (THz) emitters. Unfortunately, the nonradiative Auger recombination (AR) process is still active for massless fermions in gapless graphene. However, for massive Dirac fermions, AR can be entirely suppressed below a certain threshold of the carrier’s kinetic energy that depends on the nonparabolicity and the symmetry of the electron and hole dispersions. In this work, by finely tuning the band structure of HgCdTe quantum wells hosting massive Dirac fermions, we set the electronic system below this threshold and demonstrate that the carrier recombination is purely radiative. A coherent interband emission reaching 9.6 THz, that is to say outside the spectral range of current QCLs, is measured under these conditions, opening the way to lossless interband THz emitters.

中文翻译：

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由于俄歇抑制狄拉克费米子在 HgCdTe 量子阱中的复合，10 THz 附近的相干发射

狄拉克费米子在多种 2D 和 3D 材料中的发现以前所未有的方式推动了固态研究。在利用其特殊物理特性的众多希望中，有人认为它们减少的非辐射损失将使石墨烯在太赫兹 (THz) 发射器的竞赛中与量子级联激光器 (QCL) 竞争。不幸的是，非辐射俄歇复合 (AR) 过程对于无间隙石墨烯中的无质量费米子仍然有效。然而，对于大质量狄拉克费米子，AR 可以在低于载流子动能的某个阈值时被完全抑制，该阈值取决于电子和空穴色散的非抛物性和对称性。在这项工作中，通过微调承载大量狄拉克费米子的 HgCdTe 量子阱的能带结构，我们将电子系统设置在这个阈值以下，并证明载流子复合是纯辐射的。在这些条件下测量达到 9.6 THz 的相干带间发射，也就是说在当前 QCL 的光谱范围之外，为无损带间 THz 发射器开辟了道路。