Temperature evolution of quasiparticle dispersion dynamics in semimetallic 1T-TiTe2 via high-resolution angle-resolved photoemission spectroscopy and ultrafast optical pump-probe spectroscopy

TL;DR

This study investigates the temperature-dependent quasiparticle dispersion and dynamics in semimetallic 1T-TiTe2 using high-resolution ARPES and ultrafast spectroscopy, revealing electron-phonon interactions, flat bands, and phonon behavior.

Contribution

It provides new insights into the temperature evolution of quasiparticle features and phonon modes in 1T-TiTe2 through combined spectroscopic techniques.

Findings

Detection of a temperature-dependent kink and flat band related to electron-phonon coupling.

Identification of multiple time scales and temperature-dependent decay processes.

Observation of phonon hardening and softening with temperature and fluence.

Abstract

High-resolution angle-resolved photoemission spectroscopy and ultrafast optical pump-probe spectroscopy were used to study semimetallic 1T - TiTe2 quasiparticle dispersion and dynamics. A kink and a flat band, having the same energy scale and temperature-dependent behaviors along the G-M direction, were detected. Both manifested at low temperatures but blurred as temperature increased. The kink was formed by an electron-phonon coupling. And the localized flat band might be closely related to an electron-phonon coupling. Ultrafast optical spectroscopy identified multiple distinct time scales in the 10-300 K range. Quantitative analysis of the fastest decay process evidenced a significant lifetime temperature dependence at high temperatures, while this starts to change slowly below ~ 100 K where an anomalous Hall coefficient occurred. At low temperature, a coherent A1g phonon mode with a frequency of ~ 4.36 THz was extracted. Frequency temperature dependence suggests that phonon hardening occurs as temperature falls and anharmonic effects can explain it. Frequency fluence dependence indicates that the phonons soften as fluence increases.