Time-resolved core level photoemission reveals transient lattice distortions in $2H\mbox{-}MoTe_{2}$ crystals.

Costantini R., Cilento F., Salvador F., Morgante A., Giorgi G., Palummo M., Dell'Angela M.
  Giovedì 15/09   15:00 - 18:30   Aula D - Marianna Ciccone   II - Fisica della materia   Presentazione
In this contribution, we present the time-resolved X-ray photoemission study of a semiconductive $2H\mbox{-}MoTe_{2}$ crystal performed at the ANCHOR-SUNDYN endstation of the Elettra Synchrotron (Trieste). Upon photoexcitation, we observe a long-lived core level shift to lower binding energies that is due to the formation of surface photovoltage fields. Interestingly, in the sub-nanosecond range the photoemission peaks shift to the opposite direction, suggesting the presence of a distinct physical process at shorter timescales. With the support of DFT calculations, we modeled the deformation of the $MoTe_{2}$ lattice in the out-of-plane direction, which is along the pathway for the $2H\mbox{-}1T^{\prime}$ phase transition. Our data indicate an intermediate lattice excitation state with a measured lifetime of $\sim$ 600 ${ps}$, in which the displacement of Mo and Te atoms causes the core photoelectrons to shift to higher binding energies. These results show that high-resolution time-resolved photoemission, combined with suitable theoretical simulations, is a valuable tool for studying not only the electronic and chemical modifications of photoexcited systems, but also lattice distortions and phase transitions.