Exciton-phonon dephasing and linewidth from first-principles in monolayer MoS2
Yang-hao Chan2,6*, Jonah B. Haber1,3, Mit Naik1,3, J. B. Neaton1,3, Dinan Y. Qiu4, Felipe H. da Jornada5, Steven G. Louie3,1
1Physics, Univeristy of California, Berkeley, USA
2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
3Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, USA
4Mechanical engineering and material science, Yale University, New Haven, USA
5Material Sceince and engineering, Stanford, Stanford, CA, USA
6Physics, National Center for Theoretical Sciences, Taipei, Taiwan
* Presenter:Yang-hao Chan, email:yanghao@gate.sinica.edu.tw
Exciton-phonon interactions dominate the temperature dependence of the absorption and luminescence spectrum and determines exciton transfer rates on fs to ps time scales. However, the direct experimental measurement of exciton-phonon interaction is challenging and often subject to interpretation based on parameterized model Hamiltonians. We apply here a first-principles approach to study exciton-phonon coupling in monolayer MoS2 and reveal the highly selective nature of exciton-phonon coupling due to the internal spin structure of excitons, which leads to a surprisingly long lifetimes of the lowest energy bright A exciton. Moreover, we show that interference terms due to off-diagonal exciton-phonon matrix elements, which have thus far been neglected in first-principles studies, are critical for the description of dephasing mechanisms, and once accounted for, yield exciton linewidths in excellent agreement with experiment.

Keywords: Exciton, Phonon, 2D materials, linewidth