1] Stanford Institute for Materials and Energy Sciences (SIMES), Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA [2] HISKP University of Bonn, Bonn 53115, Germany.
Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
Nat Commun. 2015 May 11;6:7047. doi: 10.1038/ncomms8047.
Ultrafast materials science promises optical control of physical properties of solids. Continuous-wave circularly polarized laser driving was predicted to induce a light-matter coupled state with an energy gap and a quantum Hall effect, coined Floquet topological insulator. Whereas the envisioned Floquet topological insulator requires high-frequency pumping to obtain well-separated Floquet bands, a follow-up question regards the creation of Floquet-like states in graphene with realistic low-frequency laser pulses. Here we predict that short optical pulses attainable in experiments can lead to local spectral gaps and novel pseudospin textures in graphene. Pump-probe photoemission spectroscopy can track these states by measuring sizeable energy gaps and Floquet band formation on femtosecond time scales. Analysing band crossings and pseudospin textures near the Dirac points, we identify new states with optically induced nontrivial changes of sublattice mixing that leads to Berry curvature corrections of electrical transport and magnetization.
超快材料科学有望实现对固体物理性质的光学控制。连续波圆偏振激光驱动被预测会诱导出具有能隙和量子霍尔效应的光物质耦合态，被称为准拓扑绝缘体。然而，所设想的准拓扑绝缘体需要高频泵浦来获得分离良好的准带，接下来的问题是在具有实际低频激光脉冲的石墨烯中产生类似准的状态。在这里，我们预测实验中可获得的短光脉冲可以导致石墨烯中局部光谱间隙和新的赝自旋织构。泵浦探测光电子能谱可以通过在飞秒时间尺度上测量可观的能隙和准带形成来跟踪这些状态。通过分析狄拉克点附近的能带交叉和赝自旋织构，我们确定了新的状态，这些状态与亚晶格混合的光诱导非平凡变化有关，从而导致电输运和磁化的贝里曲率修正。
