Visualization of lattice dynamics and atomic motion in WSe2 monolayer

Atomically-thin materials have drawn great interest due to their exotic properties leading to a variety of promising new applications. However, the out-of-equilibrium dynamics of these materials are still not fully understood. Ultrafast electron diffraction (UED) is a powerful technique for the investigation of the transient structural dynamics of monolayers with unprecedented spatiotemporal resolution. The UED results of WSe2 monolayers are reported and the suppression of the intensity of the Bragg diffraction spots following laser excitation is attributed to electron-phonon and phonon-phonon scattering. A two-temperature model is used to accurately describe these dynamics due to the low thermal conduction of the monolayer. Furthermore, the reported lifetimes are fit using a single-mode relaxation time approximation.