Speaker
Description
We report on the application of time- and angle-resolved two-photon photoemission (2PPE) with a high-harmonic probe for the investigation of the electron dynamics in the topmost layer of bulk MoS$_2$ in momentum space. For this purpose, we have combined a high-repetition rate high-harmonic source with tunable femtosecond pump pulses and a 3D (kx, ky, E) electrostatic electron spectrometer.
We discuss the application of this setup for the investigation of the electron dynamics in the conduction band of MoS$_2$ after optical excitation with different pump photon energies. Recently, we have shown that optical excitation above the A exciton resonance at 1.8 eV with 2.05 eV pump pulses results in an immediate occupation of the conduction band at K followed by an ultrafast transfer to the conduction band minimum at Σ. Subsequently, the occupation at both high-symmetry points decays slowly on a ps timescale. We present new data for pump photon energies in the range of 1.8 to 2.3 eV and show how the dynamics of this transfer depend on the excess energy above the exciton resonance.
