论文标题
在光激发的1T-TISE $ _2 $中绘制被占用和空置的频段结构的分散
Mapping the dispersion of the occupied and unoccupied band structure in photoexcited 1T-TiSe$_2$
论文作者
论文摘要
电荷密度波（CDW）是损坏对称性的状态，并定期调制电荷和晶格，通常会导致频带结构中的间隙打开。在模型CDW系统中，1T-TISE $ _2 $此类间隙在其SE $ _ {4p} $ Valence和Ti $ _ {3D} $导出频段之间打开，并伴随着分散体的更改。这些更改对于理解CDW阶段至关重要，因为它们提供了SE $ _ {4p} $ -Ti $ _ {3D} $杂交强度和特征机械特征的度量。使用时间和角度分辨的光电子光谱（Trarpes），无占用的频带结构填充了近红外（NIR）泵脉冲，这些泵脉冲允许直接可视化抛物面形状的Ti $ _ {3d} $传导带。此外，我们观察到phothexcitation之后的SE $ _ {4p} $ Valence频段中有效质量的短暂变化。这是由于CDW相削弱而导致的总体降低，并伴随着具有特征a $ _ {1G} $ Phonon的频率的振荡组件。这些观察结果是由Trapres启用的，突出了晶格贡献在以1T-TISE $ _2 $中建立CDW订单方面的重要性。
Charge density waves (CDW) are states of broken symmetry with a periodic modulation of charge and lattice typically leading to the opening of a gap in the band structure. In the model CDW system 1T-TiSe$_2$ such a gap opens up between its Se$_{4p}$ valence and Ti$_{3d}$ conduction band, accompanied by a change of dispersion. These changes are crucial in understanding the CDW phase, as they provide a measure of the Se$_{4p}$-Ti$_{3d}$ hybridization strength and characteristic mechanistic features. Using time- and angle-resolved photoelectron spectroscopy (trARPES), the unoccupied band structure is populated with near-infrared (NIR) pump pulses which allows to to directly visualize the parabolically-shaped Ti$_{3d}$ conduction band. Furthermore, we observe a transient change of effective mass in the Se$_{4p}$ valence band following photoexcitation. This occurs alongside an overall reduction due to weakening of the CDW phase and is accompanied by an oscillating component with the frequency of the characteristic A$_{1g}$ phonon. These observations, enabled by trAPRES, highlight the importance of the lattice contributions in establishing the CDW order in 1T-TiSe$_2$.
