Zhang Xiao-Xiao, Nagaosa Naoto
RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan.
RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan; Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
Sci Bull (Beijing). 2024 Feb 15;69(3):325-333. doi: 10.1016/j.scib.2023.12.002. Epub 2023 Dec 6.
Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium. Recent experimental progress is much from optical, cold-atomic, and classical platforms due to the vast tunability and clear identification of observables. However, their counterpart in solid-state electronic systems in equilibrium remains unmasked although highly desired, where a variety of materials are available, calculations are solidly founded, and accurate spectroscopic techniques can be applied. We demonstrate that, in the surface state of a topological insulator with spin-dependent relaxation due to magnetic impurities, highly nontrivial topological soliton spin textures appear in momentum space. Such spin-channel phenomena are delicately related to the type of non-Hermiticity and correctly reveal the most robust non-Hermitian features detectable spectroscopically. Moreover, the distinct topological soliton objects can be deformed to each other, mediated by topological transitions driven by tuning across a critical direction of doped magnetism. These results not only open a solid-state avenue to exotic spin patterns via spin- and angle-resolved photoemission spectroscopy, but also inspire non-Hermitian dissipation engineering of spins in solids.
非厄米系统大多是在开放系统和非平衡的背景下进行讨论的。由于具有巨大的可调谐性和可观测量的清晰识别，近期在光学、冷原子和经典平台方面取得了很大的实验进展。然而，尽管人们非常渴望，但处于平衡态的固态电子系统中的对应物仍未被揭示，在固态电子系统中，有多种材料可供使用，计算有坚实的基础，并且可以应用精确的光谱技术。我们证明，在由于磁性杂质而具有自旋相关弛豫的拓扑绝缘体的表面态中，高度非平凡的拓扑孤子自旋纹理出现在动量空间中。这种自旋通道现象与非厄米性的类型密切相关，并正确地揭示了光谱学上可检测到的最稳健的非厄米特征。此外，不同的拓扑孤子对象可以通过在掺杂磁性的临界方向上进行调谐驱动的拓扑转变相互变形。这些结果不仅通过自旋和角分辨光电子能谱为奇异自旋模式开辟了一条固态途径，而且还激发了固体中自旋的非厄米耗散工程。
