Exciton-phonon dephasing and linewidth from first-principles in monolayer MoS2

Yang-hao Chan^2,6*, Jonah B. Haber^1,3, Mit Naik^1,3, J. B. Neaton^1,3, Dinan Y. Qiu⁴, Felipe H. da Jornada⁵, Steven G. Louie^3,1

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