The ultrafast electronic structures of the charge density wave material $1T\text{−}{\mathrm{TiSe}}_2$ were investigated by high-resolution time- and angle-resolved photoemission spectroscopy. We found that the quasiparticle populations drove ultrafast electronic phase transitions in $1T\text{−}{\mathrm{TiSe}}_2$ within 100 fs after photoexcitation, and a metastable metallic state, which was significantly different from the equilibrium normal phase, was evidenced far below the charge density wave transition temperature. Detailed time- and pump-fluence-dependent experiments revealed that the photoinduced metastable metallic state was a result of the halted motion of the atoms through the coherent electron-phonon coupling process, and the lifetime of this state was prolonged to picoseconds with the highest pump fluence used in this study. Ultrafast electronic dynamics were well captured by the time-dependent Ginzburg-Landau model. Our work demonstrates a mechanism for realizing novel electronic states by photoinducing coherent motion of atoms in the lattice.

中文翻译：

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在 1T−TiSe2 中从电荷密度波相位超快切换到亚稳态金属态

电荷密度波材料的超快电子结构$\mathrm{1个}吨\text{−}{\mathrm{硒化钛}}_{\mathrm{2个}}$通过高分辨率时间和角度分辨光电子能谱研究。我们发现准粒子群驱动超快电子相变$\mathrm{1个}吨\text{−}{\mathrm{硒化钛}}_{\mathrm{2个}}$在光激发后 100 fs 内，亚稳态金属态明显不同于平衡正相，远低于电荷密度波转变温度。详细的时间和泵注量依赖性实验表明，光致亚稳态金属态是原子通过相干电子-声子耦合过程停止运动的结果，并且这种状态的寿命在最高泵浦下延长至皮秒本研究中使用的影响力。时间相关的 Ginzburg-Landau 模型很好地捕捉了超快电子动力学。我们的工作展示了一种通过光诱导晶格中原子的相干运动来实现新电子态的机制。