近日，新加坡南洋理工大学的Y. D. Chong&Baile Zhang及其研究团队取得一项新进展。经过不懈努力，他们证实光学增益和损耗诱导出狄拉克质量。相关研究成果已于2024年7月3日在国际权威学术期刊《自然》上发表。

利用光子合成晶格，该研究团队通过实验证明了基于光学增益和损耗的非厄米摄动可以产生狄拉克质量。然后，研究人员探讨了增益和损失诱导狄拉克质量的时空工程如何影响准粒子。正如该研究所示，准粒子在空间边界处经历克莱因隧穿，但非厄米对称的局部破缺可以在畴壁处产生新的通量非守恒效应。

在狄拉克质量符号突然翻转的时间边界上，研究人员观察到时间反射现象的一种变体: 在非相对论性极限下，狄拉克准粒子的速度反转，而在相对论性极限下，原始速度保持不变。

据悉，质量通常被认为是物质的内在属性，但现代物理学揭示了粒子质量有复杂的起源，比如高能物理学中的希格斯机制。在像石墨烯这样的晶格中，相对论性狄拉克粒子可以以低能准粒子的形式存在，其质量是由晶格对称性破缺摄动赋予的。这些产生质量的机制都假定了厄米性，或者说是能量守恒。

附：英文原文

Title: Dirac mass induced by optical gain and loss

Author: Yu, Letian, Xue, Haoran, Guo, Ruixiang, Chan, Eng Aik, Terh, Yun Yong, Soci, Cesare, Zhang, Baile, Chong, Y. D.

Issue&Volume: 2024-07-03

Abstract: Mass is commonly considered an intrinsic property of matter, but modern physics reveals particle masses to have complex origins, such as the Higgs mechanism in high-energy physics. In crystal lattices such as graphene, relativistic Dirac particles can exist as low-energy quasiparticles with masses imparted by lattice symmetry-breaking perturbations. These mass-generating mechanisms all assume Hermiticity, or the conservation of energy in detail. Using a photonic synthetic lattice, we show experimentally that Dirac masses can be generated by means of non-Hermitian perturbations based on optical gain and loss. We then explore how the spacetime engineering of the gain and loss-induced Dirac mass affects the quasiparticles. As we show, the quasiparticles undergo Klein tunnelling at spatial boundaries, but a local breaking of a non-Hermitian symmetry can produce a new flux non-conservation effect at the domain walls. At a temporal boundary that abruptly flips the sign of the Dirac mass, we observe a variant of the time-reflection phenomenon: in the non-relativistic limit, the Dirac quasiparticle reverses its velocity, whereas in the relativistic limit, the original velocity is retained.

DOI: 10.1038/s41586-024-07664-x

Source: https://www.nature.com/articles/s41586-024-07664-x