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arXiv · 2211.03562

Electronic and structural fingerprints of charge density wave excitations in extreme ultraviolet transient absorption spectroscopy

Tobias Heinrich·Hung-Tzu Chang·Sergey Zayko·Kai Rossnagel·Murat Sivis·Claus Ropers
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Abstract

Femtosecond core-level transient absorption spectroscopy is utilized to investigate photoinduced dynamics of the charge density wave in 1T-TiSe2 at the Ti M2,3 edge (30-50 eV). Photoexcited carriers and phonons are found to primarily induce spectral red-shifts of core-level excitations, and a carrier relaxation time and phonon heating time of approximately 360 fs and 1.0 ps are extracted, respectively. Pronounced oscillations in delay-dependent absorption spectra are assigned to coherent excitations of the optical $A_{1g}$ phonon (6.0 THz) and the $A_{1g}^*$ charge density wave amplitude mode (3.3 THz). By comparing the measured spectra with time-dependent density functional theory simulations, we determine the directions of the momentary atomic displacements of both coherent modes and estimate their amplitudes. This work presents a first look on charge density wave excitations with table-top core-level transient absorption spectroscopy, enabling simultaneous access to electronic and lattice excitation and relaxation.

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Tobias Heinrich, Hung-Tzu Chang, Sergey Zayko, Kai Rossnagel, Murat Sivis, Claus Ropers. 2022-11-07. Electronic and structural fingerprints of charge density wave excitations in extreme ultraviolet transient absorption spectroscopy. https://arxiv.org/abs/2211.03562

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