Theory of Floquet band formation and local pseudospin textures in pump-probe photoemission of graphene
Theory of Floquet band formation and local pseudospin textures in pump-probe photoemission of graphene
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DOI：
10.1038/ncomms8047
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发表时间：
2015-05-01
影响因子：
16.6
通讯作者：
Devereaux, T. P.
中科院分区：
文献类型：
--
作者：
Sentef, M. A.;Claassen, M.;Devereaux, T. P.
超快材料科学承诺对固体的物理性质进行光学控制。预测了在连续波圆偏振激光驱动下，产生具有能隙和量子霍尔效应的光-物质耦合态，称为Floquet拓扑绝缘体。虽然设想的Floquet拓扑绝缘体需要高频泵浦以获得分离良好的Floquite带，但后续问题涉及到使用真实的低频激光脉冲在石墨烯中创建类似Floquet的状态。在这里，我们预测在实验中可以获得的短光脉冲可以导致石墨烯中的局域光谱带隙和新的伪自旋织构。泵浦探测光电子能谱可以通过在飞秒时间尺度上测量相当大的能隙和Floquit带的形成来跟踪这些状态。通过对Dirac点附近的能带交叉和赝旋织构的分析，我们发现亚晶格混合的光致非平凡变化导致了电子输运和磁化的Berry曲率修正，从而确定了新的态。
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.