We have performed ultrafast time-resolved spectroscopy of transient absorption for a thin film of Bi₃Se₂Te, in which recent study result implies the existence of topological surface state. The observed relaxation signal was attributed to the band filling and Auger recombination processes based on the pump power dependence of the signal. After the band filling, bulk-to-surface scattering is thought to proceed being mediated by phonon emission. The dynamics of the phonon was observed from the dumped oscillation appeared on the relaxation curve of the observed signal. The phase of the oscillation indicates that the phonon mode has the period of $519\pm 3$ fs in the electronic excited state.

我们已经对Bi ₃ Se ₂ Te薄膜进行了瞬态吸收的超快速时间分辨光谱，其中最近的研究结果表明存在拓扑表面状态。基于信号的泵浦功率依赖性，观察到的弛豫信号归因于谱带填充和俄歇重组过程。在带填充之后，认为从声子发射来介导从体到表面的散射。从振荡的振荡中观察到声子的动力学，出现在观察到的信号的弛豫曲线上。振荡的相位表明声子模式的周期为$519\pm 3$ fs处于电子激发状态。