论文标题
拓扑单维模型中的激子绝缘子阶段和凝结的动力学
Excitonic insulator phase and dynamics of condensate in a topological one-dimensional model
论文作者
论文摘要
我们采用平均场近似值来研究非平凡带拓扑结构与在抑制性轨道间库仑相互作用的情况下，在一维原子$ s-p $轨道的一维链中的激子绝缘子（EI）之间的相互作用。我们发现，在非相互作用的制度中，我们的模型允许拓扑和微不足道的绝缘体阶段，而在较强的库仑相互作用限制下，手性对称性被打破，系统经历了拓扑 - 脱氧绝缘体相过渡。后一个相过渡源于轨道假磁化和频段倒置在$ k = 0 $左右。我们的发现表明，与拓扑绝缘体相相反，由于缺乏带反转，电子孔结合状态不会在琐碎带绝缘子相中形成激子冷凝物。有趣的是，低$ s-p $杂交限制的EI阶段载有Bardeen-Cooper-Schrieffer（BCS）/Bose-Einstein Concensation（BEC）交叉。通过泵脉冲照射，我们的发现表明激子状态的振荡在很大程度上取决于激光脉冲的频率。我们进一步探讨了光学测量中激子冷凝物动力学的特征。
We employ mean-field approximation to investigate the interplay between the nontrivial band topology and the formation of excitonic insulator (EI) in a one-dimensional chain of atomic $s-p$ orbitals in the presence of repulsive inter-orbital Coulomb interaction. We find that our model, in a non-interacting regime, admits topological and trivial insulator phases, whereas, in strong Coulomb interaction limit, the chiral symmetry is broken and the system undergoes a topological-excitonic insulator phase transition. The latter phase transition stems from an orbital pseudomagnetization and band inversion around $k=0$. Our findings show that contrary to the topological insulator phase, electron-hole bound states do not form exciton condensate in the trivial band insulator phase due to lack of band inversion. Interestingly, the EI phase in low $s-p$ hybridization limit hosts a Bardeen-Cooper-Schrieffer (BCS)/Bose-Einstein condensation (BEC) crossover. Irradiated by a pump pulse, our findings reveal that the oscillations of exciton states strongly depend on the frequency of the laser pulse. We further explore the signatures of dynamics of the exciton condensate in optical measurements.
