Kavli Affiliate: Jeffrey B. Neaton
| First 5 Authors: Yang-hao Chan, Jonah B. Haber, Mit H. Naik, Steven G. Louie, Jeffrey B. Neaton
| Summary:
Understanding exciton thermalization is critical for optimizing
optoelectronic and photocatalytic processes in many materials. However, it is
hard to access the dynamics of such processes experimentally, especially on
systems such as monolayer transition metal dichalcogenides, where various
low-energy excitations pathways can compete for exciton thermalization. Here,
we study exciton dynamics due to exciton-phonon scattering in monolayer MoS2
from a first-principles, interacting Green’s function approach, to obtain the
relaxation and thermalization of low-energy excitons following different
initial excitations at different temperatures. We find that the thermalization
occurs on a picosecond timescale at 300 K but can increase by an order of
magnitude at 100 K. The long total thermalization time, owing to the nature of
its excitonic band structure, is dominated by slow spin-flip scattering
processes in monolayer MoS2. In contrast, thermalization of excitons in
individual spin-aligned and spin-anti-aligned channels can be achieved within a
few hundred fs when exciting higher-energy excitons. We further simulate the
intensity spectrum of time-resolved angle-resolved photoemission spectroscopy
(TR-ARPES) experiments and anticipate that such calculations may serve as a map
to correlate spectroscopic signatures with microscopic exciton dynamics.
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