Observation of photoinduced polarons in semimetal 1T-TiSe2

Yin Huang; Senhao Lv; Heyuan Liu; Qiuzhen Cheng; Yi Biao; Hongliang Lu; Xiao Lin; Zhuan Wang; Haitao Yang; Hailong Chen; Yu-Xiang Weng

doi:10.1088/1361-6528/acc188

Observation of photoinduced polarons in semimetal 1T-TiSe₂

Nanotechnology. 2023 Mar 22;34(23). doi: 10.1088/1361-6528/acc188.

Authors

Yin Huang^{1

2}, Senhao Lv¹, Heyuan Liu^{1

2}, Qiuzhen Cheng¹, Yi Biao^{1

2}, Hongliang Lu², Xiao Lin², Zhuan Wang^{1

2}, Haitao Yang^{1

2

3}, Hailong Chen^{1

2

3}, Yu-Xiang Weng^{1

2

3}

Affiliations

¹ Beijing National Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
² School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
³ Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, People's Republic of China.

PMID: 36877995
DOI: 10.1088/1361-6528/acc188

Abstract

In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe₂flakes from the high-quality single crystals with self-intercalated Ti atoms are investigated by femtosecond transient absorption spectroscopy. The observed coherent acoustic and optical phonon oscillations after ultrafast photoexcitation reveal the strong electron-phonon coupling in 1T-TiSe₂. The ultrafast carrier dynamics probed in both visible and mid-infrared regions indicate that some photogenerated carriers localize near the intercalated Ti atoms and form small polarons rapidly within several picoseconds after photoexcitation due to the strong and short-range electron-phonon coupling. The formation of polarons leads to a reduction of carrier mobility and a long-time relaxation process of photoexcited carriers for several nanoseconds. The formation and dissociation rates of the photoinduced polarons are dependent on both the pump fluence and the thickness of TiSe₂sample. This work offers new insights into the photogenerated carrier dynamics of 1T-TiSe₂, and emphasizes the effects of intercalated atoms on the electron and lattice dynamics after photoexcitation.

Keywords: electron–phonon coupling; photogenerated carrier dynamics; polaron; semimetal 1T-TiSe2; transient absorption spectroscopy.