Abstract

The last two decades have marked a revolution in materials science with the appearance of two novel groups of materials with promising features for future optoelectronics. The first are artificially fabricated metamaterials, composed of carefully engineered nanoparticle arrays, displaying tailored mie and plasmonic resonant responses [1]. The second are atomically thin two-dimensional (2D) semiconductor crystals, characterized by tightly bound excitons, promising for their flexible heterostructure stacking capabilities [2]. In this work we introduce a novel pulse-shaping approach, to study and control the coherent dynamics of resonant quasparticle excitations in such materials. By constructing a state-of-the-art pulse shaper for controlling the spectral phase of our sub-10 fs laser, we tailor the temporal order of instantaneous frequencies driving the noninstantaneous electronic response of the material on resonance [3]. We measure the response to various pulse shapes through monitoring the four-wave mixing (FWM) generation. Our contribution can be described by to three key aspects: We retrace the resonant dispersion by synchronizing the phase-dependent intra-pulse nonlinear wave-mixing with the prediction of the anharmonic oscillator model (AHO). We disentangle the multitude of interfering quantum pathways caused by the resonant dynamics, and reassemble them to achieve a strong nonlinear enhancement as well as near-complete destruction of the nonlinear yield. By controlling two successive resonant states, we present a glimpse into inter-state selectivity. We display nonlinear generation by improving the coherence in one state while suppressing the coherence in another. We believe this work places the control of coherent quasiparticle dynamics in condensed matter systems as a highly appealing field for both fundamental and applied research, such as improved nonlinear sensing, broadband compressed light sources and various ultrafast optoelectronic applications.

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