Visualization of lattice dynamics and atomic motion in WSe2 monolayer

摘要

Atomically-thin materials have drawn great interest due to their exotic propertiesleading to a variety of promising new applications. However, the out-of-equilibrium dynamics ofthese materials are still not fully understood. Ultrafast electron diffraction (UED) is a powerfultechnique for the investigation of the transient structural dynamics of monolayers withunprecedented spatiotemporal resolution. The UED results of WSe2 monolayers are reported andthe suppression of the intensity of the Bragg diffraction spots following laser excitation isattributed to electron-phonon and phonon-phonon scattering. A two-temperature model is used toaccurately 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.