Murakami Yuta, Golež Denis, Eckstein Martin, Werner Philipp
Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland.
Department of Physics, University of Erlangen-Nürnberg, 91058 Erlangen, Germany.
Phys Rev Lett. 2017 Dec 15;119(24):247601. doi: 10.1103/PhysRevLett.119.247601.
We study the dynamics of excitonic insulators coupled to phonons using the time-dependent mean-field theory. Without phonon couplings, the linear response is given by the damped amplitude oscillations of the order parameter with a frequency equal to the minimum band gap. A phonon coupling to the interband transfer integral induces two types of long-lived collective oscillations of the amplitude, one originating from the phonon dynamics and the other from the phase mode, which becomes massive. We show that, even for small phonon coupling, a photoinduced enhancement of the exciton condensation and the gap can be realized. Using the Anderson pseudospin picture, we argue that the origin of the enhancement is a cooperative effect of the massive phase mode and the Hartree shift induced by the photoexcitation. We also discuss how the enhancement of the order and the collective modes can be observed with time-resolved photoemission spectroscopy.
我们使用含时平均场理论研究了与声子耦合的激子绝缘体的动力学。在没有声子耦合的情况下，线性响应由序参量的阻尼振幅振荡给出，其频率等于最小带隙。声子与带间转移积分的耦合会引发两种长寿命的振幅集体振荡，一种源于声子动力学，另一种源于变为有质量的相位模式。我们表明，即使对于小的声子耦合，也可以实现光致激子凝聚和能隙的增强。利用安德森赝自旋图像，我们认为增强的起源是有质量的相位模式和光激发诱导的哈特里位移的协同效应。我们还讨论了如何通过时间分辨光电子能谱观察序参量和集体模式的增强。
