Surface asymmetry induced turn-overed lifetime of acoustic phonons in monolayer MoSSe

Xuefei Yan; Xiangyue Cui; Bowen Wang; Hejin Yan; Yongqing Cai; Qingqing Ke

doi:10.1016/j.isci.2023.106731

Surface asymmetry induced turn-overed lifetime of acoustic phonons in monolayer MoSSe

iScience. 2023 Apr 28;26(5):106731. doi: 10.1016/j.isci.2023.106731. eCollection 2023 May 19.

Authors

Xuefei Yan^{1

2

3}, Xiangyue Cui³, Bowen Wang³, Hejin Yan³, Yongqing Cai³, Qingqing Ke^{1

2}

Affiliations

¹ School of Microelectronics Science and Technology, Sun Yat-Sen University, Zhuhai 519082, People's Republic of China.
² Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-Sen University, Zhuhai 519082, People's Republic of China.
³ Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, People's Republic of China.

Abstract

Recent successful growth of asymmetric transition metal dichalcogenides via accurate manipulation of different chalcogen atoms in top and bottom surfaces demonstrates exotic electronic and chemical properties in such Janus systems. Within the framework of density functional perturbation theory, anharmonic phonon properties of monolayer Janus MoSSe sheet are explored. By considering three-phonons scattering, out-of-plane flexural acoustic (ZA) mode tends to undergo a stronger phonon scattering than transverse acoustic (TA) mode and the longitudinal acoustic (LA) mode with phonon lifetime of ZA (1.0 ps) < LA (23.8 ps) < TA (25.8 ps). This is sharply different from the symmetric MoS₂ where flexural ZA mode has the weakest anharmonicity and is least scattered. Moreover, utilizing non-equilibrium Green function method, ballistic thermal conductance at room temperature is found to be around 0.11 nWK^-1nm^-2, lower than that of MoS₂. Our work highlights intriguing phononic properties of such MoSSe Janus layers associated with asymmetric surfaces.

Keywords: Acoustic property; Materials property; Physics.