In this work, we use ultrafast pump-probe nonresonant and resonant x-ray diffraction to track the periodic lattice distortion and the electronic charge density wave in $1\mathrm{T}\text{−}{\mathrm{TiSe}}_2$ upon optical excitation. We observe a fluence regime in which the periodic lattice deformation is strongly suppressed but the charge density wave related Se $4p$ orbital order remains mostly intact. Complete melting of both structural and electronic order occurs four to five times faster than expected from a purely electronic charge-screening process, strongly suggesting a structurally assisted weakening of excitonic correlations. Our experimental data provide insight on the intricate coupling between structural and electronic order in stabilizing the periodic-lattice-distortion/charge-density-wave state in $1\mathrm{T}\text{−}{\mathrm{TiSe}}_2$. The results further show that electron-phonon coupling can lead to different, energy dependent phase-transition pathways in condensed matter systems, opening different possibilities in the conception of nonequilibrium phenomena at the ultrafast scale.

中文翻译：

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结构参与1T-TiSe2中电荷密度波的熔化

在这项工作中，我们使用超快泵浦非共振和共振X射线衍射技术来跟踪周期性的晶格畸变和电子电荷密度波。 $\mathrm{1个}\mathrm{Ť}\text{-}{\mathrm{钛硒}}_2$在光激发下。我们观察到一种注量状态，其中周期性的晶格变形被强烈抑制，但电荷密度波与硒有关$4p$轨道秩序基本保持不变。结构和电子顺序的完全熔化比纯电子电荷筛选过程预期的快四到五倍，这强烈暗示了结构辅助的激子相关性减弱。我们的实验数据为稳定结构中的周期性晶格畸变/电荷密度波状态提供了结构和电子顺序之间复杂耦合的见解。$\mathrm{1个}\mathrm{Ť}\text{-}{\mathrm{钛硒}}_2$。结果进一步表明，电子-声子耦合可导致凝聚态系统中不同的，取决于能量的相变路径，从而在超快速尺度上为非平衡现象的概念打开了不同的可能性。