Mapping the dispersion of the occupied and unoccupied band structure in photoexcited 1T-TiSe2
Mapping the dispersion of the occupied and unoccupied band structure in photoexcited 1T-TiSe2
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DOI：
10.1016/j.jpcs.2022.110740
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发表时间：
2022-04
影响因子：
4
通讯作者：
Maximilian Huber;Y. Lin;N. Dale;R. Sailus;S. Tongay;R. Kaindl;A. Lanzara
中科院分区：
文献类型：
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作者：
Maximilian Huber;Y. Lin;N. Dale;R. Sailus;S. Tongay;R. Kaindl;A. Lanzara
电荷密度波（CDW）是对称性破缺的状态，其具有电荷和晶格的周期性调制，通常导致带结构中的间隙打开。在模型CDW系统1 T-TiSe_2中，Se_4价带和Ti_3导带之间出现了能隙，并伴随着色散的变化。这些变化对于理解CDW相是至关重要的，因为它们提供了Se 4p-Ti 3d杂化强度和特征机械特征的测量。使用时间和角度分辨光电子能谱（trARPES），未占用的能带结构填充近红外（NIR）泵浦脉冲，允许直接可视化的抛物线形状的Ti 3d导带。此外，我们观察到的有效质量的瞬态变化在Se 4 pvalence带以下的光激发。这发生在由于CDW相的减弱而导致的整体减少的旁边，并且伴随着具有特征A1声子频率的振荡分量。这些观测结果，启用trAPRES，突出了晶格贡献的重要性，在建立CDW秩序在1 T-TiSe 2。
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-TiSe2such a gap opens up between its Se4pvalence and Ti3dconduction band, accompanied by a change of dispersion. These changes are crucial in understanding the CDW phase, as they provide a measure of the Se4p-Ti3dhybridization 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 directly visualize the parabolically-shaped Ti3dconduction band. Furthermore, we observe a transient change of effective mass in the Se4pvalence 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 A1gphonon. These observations, enabled by trAPRES, highlight the importance of the lattice contributions in establishing the CDW order in 1T-TiSe2.