Ultrafast dynamics in SnS crystals
Nguyen Nhat Quyen1*, Wen Yen Tzeng1, C. N. Kuo2, C. S. Lue2, Chih Wei Luo1,3,4
1Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
2Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
3Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
4Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 30010, Taiwan
* Presenter:Nguyen Nhat Quyen, email:nhatquyen126@gmail.com
Tin sulfide (SnS) is one of the promising materials for the applications of optoelectronics and photovoltaics. Herein, the ultrafast dynamics of photo-excited electrons and phonons in SnS single crystals have been studied using dual-color transient reflectivity change (R/R) measurements at various temperatures. Besides the several- and several tens-ps relaxation processes, an interesting damped oscillation component with frequency of GHz was also observed in R/R. In addition, the anisotropic and temperature-dependent carrier decay dynamics were also observed by measuring the polarization-resolved transient absorption. The damping of the coherent acoustic phonon oscillation was found to be anisotropic, which is due to the polarization-dependent absorption length of the probe pulse. Based on the qualitative analysis of initial oscillation amplitude and phase of coherent acoustic phonon oscillation, we suggested that the direct deformation potential mechanism affects the generation of coherent acoustic phonons. These results provide significant insights into the acoustic phonon properties of SnS and promise an important application for SnS in polarization-sensitive optical and optoelectronic devices.

Keywords: SnS single crystal, anisotropic, ultrafast dynamics