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arXiv · 1607.04999

Intervalley scattering in MoS$_2$ imaged by two-photon photoemission with a high-harmonic probe

Robert Wallauer·Johannes Reimann·Nico Armbrust·Jens Güdde·Ulrich Höfer
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Abstract

We report on the direct mapping of electron transfer in the momentum space of bulk MoS$_2$ by means of time- and angle-resolved two-photon photoemission with a high-harmonic probe. For this purpose, we have combined a high-repetition rate high-harmonic source with tunable femtosecond pump pulses and a 3D ($k_x, k_y, E$) electron spectrometer. We show that optical excitation slightly above the A exciton resonance results in an immediate occupation of the conduction band at $\overline{K}$ followed by an ultrafast transfer ($< 50$~fs) to the conduction band minimum at $\overlineΣ$. Both signals, at $\overline{K}$ and $\overlineΣ$, do not vanish over the observed period of 400~fs. The technique described here enables direct access to the charge transfer dynamics in $k$-space and allows the study of decay times and decay channels in various systems with dependence on the excess energy or helicity of the excitation.

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Robert Wallauer, Johannes Reimann, Nico Armbrust, Jens Güdde, Ulrich Höfer. 2016-10-13. Intervalley scattering in MoS$_2$ imaged by two-photon photoemission with a high-harmonic probe. https://doi.org/10.1063/1.4965839

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