Zhang Xiao-Xiao, Nagaosa Naoto
RIKEN Center for Emergent Matter Science (CEMS), Saitama 351-0198, Japan.
Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan.
Proc Natl Acad Sci U S A. 2022 Mar 22;119(12):e2116976119. doi: 10.1073/pnas.2116976119. Epub 2022 Mar 18.
SignificanceOptically excited systems can host unprecedented phenomena and reveal key information. The spin-channel physics in the photoexcited dynamics of quantum matter remains largely unexplored. This study finds the topological surface state under contemporary time-resolved pump-probe spectroscopy an exceptionally capable platform in this regard. Spin signals exhibit interesting tornado-like spiral patterns, and the unusual topological optical activity can be indicative of spintronic applications. This exemplifies a purely nonequilibrium topological winding phenomenon, where all the hidden helicity factors in the light-matter-coupled system are robustly encoded. These results open a direction of nonequilibrium topological spin states in quantum materials.
意义
光激发系统能够呈现前所未有的现象并揭示关键信息。量子物质光激发动力学中的自旋通道物理在很大程度上仍未被探索。本研究发现，在当代时间分辨泵浦 - 探测光谱学下，拓扑表面态在这方面是一个极具能力的平台。自旋信号呈现出有趣的龙卷风状螺旋图案，并且这种不寻常的拓扑光学活性可用于自旋电子学应用。这例证了一种纯粹的非平衡拓扑缠绕现象，其中光 - 物质耦合系统中所有隐藏的螺旋度因素都被稳健地编码。这些结果为量子材料中的非平衡拓扑自旋态开辟了一个方向。
