发表机构
Max-Born-Institute for Non-Linear Optics; Institute for Theoretical Solid-State Physics, Freie Universität Berlin; Scientific Computing Department, Science and Technology Facilities Council UK Research and Innovation (STFC-UKRI), Rutherford Appleton Laboratory（马克斯·玻恩非线性光学研究所; 柏林自由大学理论凝聚态物理研究所; 英国研究与创新科学技术设施委员会（STFC-UKRI）拉瑟福德阿普尔顿实验室科学计算部）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文发展了周期固体中轨道角动量的一般算符理论，适用于平衡与非平衡态，揭示了激光驱动下超快非平衡OAM现象，为光控OAM和拓扑能带设计提供了新途径。
AI 中文摘要
我们发展了周期固体中轨道角动量（OAM）的一般算符理论，该理论同样适用于平衡态和相干驱动态。利用Adams和Blount的晶体动量表示，我们构造了一个周期固体OAM算符，它精确对应于对称化的$\nhat{\mathbf r}\times\hat{\mathbf v}$可观测量，并证明该算符可分解为局域环流（LC）和迁移环流（IC）两个部分，它们都是厄米的，且在$U(1)$以及更一般的$U(N)$规范变换下协变。在平衡态下，LC和IC部分归结为已建立的轨道磁性现代理论；在非平衡态下，相同的算符结构揭示了由激光写入的动量空间纹理和带间相干性产生的新贡献。应用于带隙石墨烯时，我们发现了丰富的超快非平衡轨道角动量现象，包括准静态的光诱导OAM。这后一发现，基于能带流形相位纹理与非平衡OAM之间的紧密联系，指出了通过光控制固体中OAM的新可能性，以及拓扑能带结构在设计OAM材料中可能发挥的丰富作用。
英文摘要
We develop a general operator theory of orbital angular momentum (OAM) in periodic solids that applies equally to equilibrium and coherently driven states. Employing the crystal momentum representation of Adams and Blount, we construct a periodic-solid OAM operator exactly corresponding to the symmetrized $\hat{\mathbf r}\times\hat{\mathbf v}$ observable, and show that it separates into local circulation (LC) and itinerant circulation (IC) sectors that are Hermitian and $U(1)$, and more generally $U(N)$, gauge covariant. In equilibrium, the LC and IC sectors reduce to the established modern theory of orbital magnetism; out of equilibrium, the same operator structure exposes new contributions generated by laser-written momentum-space textures and interband coherence. Applied to gapped graphene, we uncover a rich phenomenology of ultrafast non-equilibrium orbital angular momentum, including a quasi-stationary light-induced OAM. This latter finding, underpinned by a close connection between band-manifold phase texture and nonequilibrium OAM, points towards new possibilities for light control over OAM in solids as well as a potentially rich role for topological band structures in designed OAM materials.
