Temperature evolution of quasiparticle dispersion and dynamics in semimetallic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>TiTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> via high-resolution angle-resolved photoemission spectroscopy and ultrafast optical pump-probe spectroscopy
Shuang-Xing Zhu, Chen Zhang, Qi-Yi Wu, Xiaofang Tang, Hao Liu, Ziteng Liu, Yang Luo, Jiao-Jiao Song, Fan-Ying Wu, Yin-Zou Zhao, Shu-Yu Liu, Tian Le, Xin Lü, He Ma, Kaihui Liu, Yahua Yuan, Han Huang, Jun He, Haiyun Liu, Yu-Xia Duan, Jian-Qiao Meng
Abstract
High-resolution angle-resolved photoemission spectroscopy and ultrafast optical pump-probe spectroscopy were used to study semimetallic $1T\ensuremath{-}{\mathrm{TiTe}}_{2}$ quasiparticle dispersion and dynamics. A kink and a flat band, having the same energy scale and temperature-dependent behaviors along the $\overline{\mathrm{\ensuremath{\Gamma}}}\text{\ensuremath{-}}\overline{M}$ 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 $\ensuremath{\sim}100$ K where an anomalous Hall coefficient occurred. At low temperature, a coherent ${A}_{1}g$ phonon mode with a frequency of $\ensuremath{\sim}4.36$ 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.