Mapping the dispersion of the occupied and unoccupied band structure in photoexcited 1T-TiSe${}_2$

Abstract

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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Cited by in corpus (4)

• Time- and Angle-Resolved Photoemission Studies of Quantum Materials
• Advancing time- and angle-resolved photoemission spectroscopy: The role of ultrafast laser development
• Ultrafast creation of a light induced semimetallic state in strongly excited 1T-TiSe${}_2$
• Carrier-Density Control of the Quantum-Confined 1$T$-TiSe${}_2$ Charge-Density-Wave