双轨道哈伯德模型中激子有序和Rabi振荡的光诱导动力学
Photoinduced dynamics of excitonic order and Rabi oscillation in the two-orbital Hubbard model
摘要：
我们研究了双轨道哈伯德模型中激子有序光诱导增强的条件，这在我们以前的工作[Phys. Rev. B 97，115105（2018）]中已经从理论上提出，并从拉比振荡的角度进行了分析。在平均场近似下，我们模拟了具有直接带隙的激子绝缘体的实时动力学，其中初始状态下的对凝聚具有BEC性质，光激发由电偶极跃迁引入。我们首先讨论了在原子极限下，我们的模型被简化为一个经历拉比振荡的二能级系统，使得对于单周期脉冲，光照射后的物理量基本上由拉比频率与泵浦光频率之比决定。然后，它表明，即使在非零的转移积分的情况下，每个单粒子状态表现出拉比振荡导致的激子阶的增强，这张照片举行。我们证明，电子-声子相互作用的影响不改变定性的结果。我们还研究了多体动力学的精确对角化方法对小集群，这强烈表明，我们的机制增强的激子顺序生存，即使考虑到量子涨落。
英文摘要：
We investigate the condition for the photoinduced enhancement of an excitonic order in a two-orbital Hubbard model, which has been theoretically proposed in our previous work [Phys. Rev. B 97, 115105 (2018)], and analyze it from the viewpoint of the Rabi oscillation. Within the mean-field approximation, we simulate real-time dynamics of an excitonic insulator with a direct gap, where the pair condensation in the initial state is of BEC nature and the photoexcitation is introduced by electric dipole transitions. We first discuss that in the atomic limit our model is reduced to a two-level system that undergoes the Rabi oscillation, so that for single cycle pulses physical quantities after the photoirradiation are essentially determined by the ratio of the Rabi frequency to the pump-light frequency. Then, it is shown that this picture holds even in the case of nonzero transfer integrals where each one-particle state exhibits the Rabi oscillation leading to the enhancement of the excitonic order. We demonstrate that effects of electron-phonon interactions do not alter the results qualitatively. We also examine many-body dynamics by the exact diagonalization method on small clusters, which strongly suggests that our mechanism for the enhancement of the exctionic order survives even when quantum fluctuations are taken into account.
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