Amalya Johnson, Stanford University
Abstract:
When photoexcitation creates charge carriers in TMDC van der Waals heterostructures, phonons will be emitted through electron-phonon coupling during charge carrier scattering and relaxation. After that, further heat exchange and thermalization will occur between the layers. Using ultrafast electron diffraction, photoinduced phonon dynamics are directly revealed in MoS2/WS2 and WSe2/MoSe2 twisted heterobilayers. Upon photoexcitation, the initial charge carrier transfer and relaxation leads to ≤ 1 ps ultrafast lattice heating in each layer of the heterobilayer. Subsequently, we identified a distinct heat transfer channel between the two layers that appears on the order of 20 ps after photoexcitation. We further identified the dependence of this heat transfer rate on heterobilayer twist angles. This experimentally determined heat transfer rate was found to occur up to an order of magnitude faster than predicted in a fully thermalized model. This heat transfer is likely facilitated by the initial nonthermal phonon distribution from carrier scattering and relaxation. Quantitative determination of the ultrafast lattice dynamics across TMDC interfaces is an essential key in understanding the structure-property relationships of 2D heterobilayers. These findings will have direct applications in the design and fabrication of 2D material quantum devices in the future.
Poster Session Link: https://gather.town/invite?token=0pEoq7VP
If you have any questions for the presenter, please contact them via email: amalyaj@stanford.edu