Charge-density wave amplitude mode in 1T-TiSe2 probed by core-level transient absorption spectroscopy

Abstract

We use high-sensitivity ultrafast high-harmonic spectroscopy to track coherent phonons in the charge-density wave phase of 1T-TiSe2. Using harmonics near the Ti-M-edge, we distinguish spectral signatures of the 3.3-THz amplitude mode and 6-THz optical phonons.

Carrier and Phonon Dynamics in Multilayer WSe2 Captured by Extreme Ultraviolet Transient Absorption Spectroscopy

“…For example, when many-body interactions between the core-level-to-CB and VB-to-CB excitations become non-negligible, the static extended edge absorption may include contributions from both core-level-to-CB and VB-to-CB transitions. 39,40 In this case, the optically excited electrons occupying the orbitals above the Fermi level affect not only the one-particle transitions from the core level but also the many-body transitions consisting of both corelevel transitions and valence excitations, leading to TA signals in the extended edge region. Note that such an effect is not applicable to the hole feature as energy conservation dictates that in the pre-edge region; only the mixing of core-to-VB and inner-VB transitions can have major contributions when manybody effects are significant.…”

Disentangle electronic, structural, and spin dynamics using transient extreme ultraviolet spectroscopy

“…17,93–97 On the other hand, coherent phonons often appear as spectral oscillations in the transient XUV spectra. 80,85,98,125 In a multi-element compound where different elemental absorptions are simultaneously measured, coherent phonon dynamics may behave differently for different elements. 85 Combining with the underlying lattice structures and theoretical calculations, a detailed understanding of the coherent phonon dynamics, such as the atomic displacement amplitude and phase, electron–phonon coupling, and phonon–phonon scattering can be reconstructed.…”

“…In addition to local lattice distortion, transient XUV spectroscopy can also measure the excitation of coherent phonons in solids. 50,80,85,125 Coherent phonons often manifest as oscillating spectral signals with well-defined frequencies in transient XUV spectroscopy. 50,80,85,125 Compared to optical spectroscopy, there are several technical advantages of using transient XUV spectroscopy to study coherent phonon dynamics.…”

“…50,80,85,125 Coherent phonons often manifest as oscillating spectral signals with well-defined frequencies in transient XUV spectroscopy. 50,80,85,125 Compared to optical spectroscopy, there are several technical advantages of using transient XUV spectroscopy to study coherent phonon dynamics. First, transient XUV spectroscopy measures element-specific phonon dynamics.…”

“…First, transient XUV spectroscopy measures element-specific phonon dynamics. 85,125 Fundamentally, phonon vibrations modify inter-atomic distances, which could result in a change in the core-to-valence XUV transition energy. With element specificity in phonon spectra, it is potentially easier to identify the phonon modes involved.…”