Nonequilibrium susceptibility in photoinduced Floquet states is studied. We analyze an electron system coupled with a heat bath in a time-periodic oscillating electric field. Spin/charge susceptibility is formulated on the basis of the Floquet Green function method, and is calculated numerically in a wide range of amplitude and frequency of light. When the frequency is larger than the bandwidth, the susceptibility is enhanced due to the dynamical localization effect, and their peak positions in the momentum space are shifted by the Fermi surface deformation. In the case of the small frequency and amplitude, multiple-peak structure emerges in the susceptibility, originating from the multiple Floquet bands which cross the Fermi level. To confirm those numerical results and provide the interpretation, an approximated expression of the susceptibility is derived for small electric-field amplitude.
Floquet theory of photoinduced topological phase transitions in the organic salt $α$-(BEDT-TTF)$_2$I$_3$ irradiated with elliptically polarized light
本文从理论上研究了在单轴压力下有机盐$α$ -（BEDT-TTF）$_2$ I $_3$中可能发生的光致拓扑相变。Floquet分析的驱动紧束缚模型，这种材料揭示了丰富的光致变化的能带结构，陈数，霍尔电导率照射下的椭圆偏振光。所得到的相图包含多种非平衡稳定相，例如，Floquet Chern绝缘子、Floquet半金属和Floquet正常绝缘子相。这一工作拓宽了光致拓扑相变研究的目标材料范围，并有助于物质中电子态的光学操纵研究的发展。
Real-time dynamics of the photoinduced topological state in organic conductor $α$-(BEDT-TTF)$_2$I$_3$ under continuous-wave and pulse excitations
我们从理论上研究了最近用Floquet理论预测的有机导体$α$ -（BEDT-TTF）$_2$ I $_3$中光致拓扑相变到非平衡Floquet Chern绝缘体的实时动力学。利用紧束缚模型$α$ -（BEDT-TTF）$_2$ I $_3$，求解了含时薛定谔方程，得到了圆偏振光连续波和脉冲激发下的物理量随时间的演化.我们证明，对于连续波激发，陈数和霍尔电导率的时间曲线显示Floquet拓扑绝缘体的迹象。我们认为，霍尔电导率表现出一个缓慢的振荡，其频率对应于由Floquet带结构确定的光致直接间隙。在脉冲激发下，得到了瞬态激发谱，据此我们推测了脉冲辐照过程中Floquet带的形成和狄拉克点处的能隙开放。这种动态间隙的形成也表现为霍尔电导率的缓慢振荡分量;也就是说，它的频率随着时间的推移而增加，朝向脉冲峰值，在该脉冲峰值处，它几乎与光致直接间隙重合。实验结果的相关性进行了讨论。
Predicted photoinduced pair annihilation of emergent magnetic charges in the organic salt $α$-(BEDT-TTF)$_2$I$_3$ irradiated by linearly polarized light
长期的实验尝试，以找到磁单极子（即，在三维空间中具有孤立磁荷的基本粒子）尚未成功，尽管自1931年狄拉克提出以来进行了大量的努力。粒子物理学家已经预言了两个符号相反的磁荷可能发生碰撞和对湮灭。然而，如果这种湮灭存在，它的实验观测将是困难的，因为它的能量尺度被预测为非常高（$\sim$ 10 $^{16}$ GeV）。在目前的工作中，我们理论上预测使用Floquet理论，一对轻微的带隙的Dirac锥带在弱电荷有序的有机导体$α$ -（BEDT-TTF）$_2$ I $_3$，这表现为磁荷在动量空间中具有相反的符号，表现出对湮灭线偏振光照射下。这种光致对湮灭是伴随着一个非拓扑相变的Floquet正常绝缘体相的对比，众所周知的圆偏振光诱导的拓扑相变的Floquet陈省身绝缘体相。我们讨论了$α$ -（BEDT-TTF）$_2$ I $_3$具有能够实现合适的实验条件（即，非共振条件）和提供所需交错位置电势的电荷有序状态，从而提供了可用于观察预测的对湮灭现象的材料的罕见实例。并对实验观测的可行性进行了讨论。
Multiple Floquet Chern insulator phases in the spin-charge coupled triangular-lattice ferrimagnet: Crucial role of higher-order terms in the high-frequency expansion
Nonequilibrium steady states in driven holographic Weyl semi-metals
Wilczek Quantum Center, School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；InQubator for Quantum Simulation (IQuS), Department of Physics, University of Washington（华盛顿大学物理学部量子模拟创新中心）；Department of Mathematics, University of Michigan（密歇根大学数学系）
Many-body correlations in Floquet steady-states: Frequency-resolved renormalization group of the driven Anderson impurity
RWTH Aachen University（亚琛工业大学）；Technische Universität Braunschweig（布伦瑞克工业大学）；Max Planck Institute for the Structure and Dynamics of Matter（马普物质结构动力学研究所）
