Van der Waals (vdW) heterostructures of transition-metal dichalcogenide (TMD) semiconductors are central not only for fundamental science, but also for electro- and optical-device technologies where the interfacial charge transfer is a key factor. Ultrafast interfacial charge dynamics has been intensively studied, however, the atomic scale insights into the effects of the electron-phonon (e-p) coupling are still lacking. In this paper, using time dependent ab initio nonadiabatic molecular dynamics, we study the ultrafast interfacial charge transfer dynamics of two different TMD heterostructures ${\mathrm{MoS}}_2/{\mathrm{WS}}_2$ and ${\mathrm{MoSe}}_2/{\mathrm{WSe}}_2$, which have similar band structures but different phonon frequencies. We found that ${\mathrm{MoSe}}_2/{\mathrm{WSe}}_2$ has softer phonon modes compared to ${\mathrm{MoS}}_2/{\mathrm{WS}}_2$, and thus phonon-coupled charge oscillation can be excited with sufficient phonon excitations at room temperature. In contrast, for ${\mathrm{MoS}}_2/{\mathrm{WS}}_2$, phonon-coupled interlayer charge oscillations are not easily excitable. Our study provides an atomic level understanding on how the phonon excitation and e-p coupling affect the interlayer charge transfer dynamics, which is valuable for both the fundamental understanding of ultrafast dynamics at vdW hetero-interfaces and the design of novel quasi-two-dimensional devices for optoelectronic and photovoltaic applications.

• Received 8 September 2017
• Revised 16 April 2018

DOI:https://doi.org/10.1103/PhysRevB.97.205417