Kavli Affiliate: Alessandra Lanzara
| First 5 Authors: Maximilian Huber, Yi Lin, Nicholas Dale, Renee Sailus, Sefaattin Tongay
| Summary:
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$_2$.
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