Temperature Effects on Optical Spectra of Monolayer MoS2

We present the effects of temperature on the electronic structure and optical spectra of monolayer MoS2. Newly measured optical absorption and photoluminescence spectra reveal substantial frequency shifts of exciton peaks as monolayer MoS2 is cooled from 300 K to 4 K. First-principles simulations using the GW-Bethe Salpeter Equation approach satisfactorily reproduce these frequency shifts by incorporating the thermal expansion. Studying these temperature effects in monolayer MoS2 is crucial for rectifying the results of room-temperature experiments with the previous predictions of zero-temperature-limit simulations. Additionally, we show that tracking the frequency shifts in the exciton peak of optical spectra may serve as a convenient way of estimating thermal expansion coefficients in two-dimensional chalcogenides.