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O: Fachverband Oberflächenphysik

O 80: Ultrafast Electron Dynamics at Surfaces and Interfaces I

O 80.9: Vortrag

Donnerstag, 4. April 2019, 12:30–12:45, H16

Inter- and intralayer electron dynamics in MoS₂ probed by 2PPE — •Robert Wallauer, Johannes Reimann, Jens Güdde, and Ulrich Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35037 Marburg

We use time- and angle-resolved two photon photoemission (2PPE) with a high-harmonic probe for the investigation of electron dynamics of MoS₂ in momentum space. For this purpose, we combined a high-repetition rate high-harmonic source with a 3D (k_x, k_y, E) electrostatic electron spectrometer [1]. The pump laser is tunable within the visible from around 500 - 700 nm. At our high-harmonic photon energy of 23.5 eV we essentially probe only the first layer, which differs from the bulk with respect to band energies.

By tuning our pump laser above and below the band gap of the first layer we are able to selectively induce the excitation from the valence into the conduction band at K within the first layer or alternatively in deeper layers. For all photon energies, the relaxation to the conduction band minimum at Σ is observed. The relaxation dynamics, however, varies with pump photon energy, which allows us to distinguish between charge transfer within the first layer and charge transfer between adjacent layers.

[1] R. Wallauer et al., Appl. Phys. Lett. 109, 162102 (2016).