Ultrafast excitation and topological soliton formation in incommensurate charge density wave states
Ultrafast excitation and topological soliton formation in incommensurate charge density wave states
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DOI：
10.1103/physrevb.104.125132
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发表时间：
2021-09
影响因子：
3.7
通讯作者：
Xiao-Xiao Zhang-Xiao;D. Manske;N. Nagaosa
中科院分区：
文献类型：
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作者：
Xiao-Xiao Zhang-Xiao;D. Manske;N. Nagaosa
拓扑孤子是公度密度波态中的非微扰激发，它连接着简并的基态。在无公度密度波态下，基态不断简并，拓扑孤子被认为与微扰相激子的激发是光滑连接的。研究了无公度电荷密度波基态一维链中光激发电子-空穴对的超快非平衡动力学。时间分辨演化揭示了集体模的微扰激发和由于产生新的拓扑孤子而产生的非微扰拓扑相变，其中连续的复序参数与幅度和相位是必不可少的。我们在复平面中识别出这种非平衡态所特有的非平凡的绕相孤子，并用一个低能有效模型来捕获它。微扰的时间带隙振荡和孤子带隙内态进入光导吸收边和与光谱测量相关的光谱密度，为实际实验提供了具体的联系。
Topological soliton is a nonperturbative excitation in commensurate density wave states and connects degenerate ground states. In incommensurate density wave states, ground states are continuously degenerate and topological soliton is reckoned to be smoothly connected to the perturbative phason excitation. We study the ultrafast nonequilibrium dynamics due to photoexcited electron-hole pair in a one-dimensional chain with an incommensurate charge density wave ground state. Time-resolved evolution reveals both perturbative excitation of collective modes and nonperturbative topological phase transition due to creating novel topological solitons, where the continuous complex order parameter with amplitude and phase is essential. We identify the nontrivial phase-winding solitons in the complex plane unique to this nonequilibrium state and capture it by a low-energy effective model. The perturbative temporal gap oscillation and the solitonic in-gap states enter the optical conductivity absorption edge and the spectral density related to spectroscopic measurement, providing concrete connections to real experiments.