Sub-cycle valleytronics: control of valley polarization using few-cycle linearly polarized pulses

So far, it has been assumed that selective excitation of a desired valley in the Brillouin zone of a hexagonal two-dimensional material has to rely on using circularly polarized fields. We theoretically demonstrate away to control the valley excitation in hexagonal 2D materials on a few-femtosecond timescale using a few-cycle, linearly polarized pulse with controlled carrier-envelope phase. The valley polarization is mapped onto the strength of the perpendicular harmonic signal of a weak, linearly polarized pulse, which allows to read this information all-optically without destroying the valley state and without relying on the Berry curvature, making our approach potentially applicable to inversion-symmetric materials. We show applicability of this method to hexagonal boron nitride and MoS2. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement