High harmonic generation in monolayer MoS2 controlled by resonant and near-resonant pulses on ultrashort time scales
Pavel Peterka, A. O. Slobodeniuk, Tomáš Novotný, Pawan Suthar, Miroslav Bartoš, F. Trojánek, P. Malý, Martin Kozák
Abstract
We report on experimental investigation of nonperturbative high harmonic generation (HHG) in monolayer MoS2 in the ultraviolet spectral region driven by mid-infrared light. We study how the HHG is influenced by pre-excitation of the monolayer using resonant and near-resonant pulses in a pump–probe-like scheme. The resonant light creates high density exciton population. Due to ultrafast dephasing caused by electron–electron scattering, the HHG is suppressed in the presence of pre-excited carriers. In the case of near-resonant excitation with photon energy below the exciton transition, the dynamics of the observed suppression of the HHG yield contains a fast component, which is a consequence of momentum scattering at carriers, which are excited by two-photon transition when the two pulses temporally overlap in the sample. This interpretation is supported by comparing the experimental data with theoretical calculations of the two-photon absorption spectrum of the MoS2 monolayer. This work demonstrates a possibility to control HHG in low-dimensional materials on ultrashort timescales by combining the driving strong-field pulse with a weak near-resonant light.