Carrier-envelope phase and off-resonant light-controlled electron dynamics in monolayer WSe2

Abstract

We theoretically study the interaction of an irradiated ultrafast laser pulse with Dirac fermions in monolayer WSe2 coupled with an off-resonant light. The optical pulse has a duration of a few femtoseconds and an amplitude of the order 0.1 - 1 V angstrom(-1). Because the electron scattering time is more than the duration of the laser pulse, the electron dynamics driven by the electric field are coherent, and can be described by the time-dependent Schrodinger equation. The two proposed waveforms are described by the Gaussian and Legendre-Gaussian polynomial associated with a carrier-envelope phase (CEP). Quantum electron dynamics in monolayer WSe2 are highly nonadiabatic, which implies electron transition from the valence band to the conduction band to be deeply irreversible. In particular, we investigate the impact of off-resonant light and CEP on the conduction band population. We show that the electron distribution in reciprocal space represents asymmetric hot spots at the Dirac points, and this strongly depends on the CEP. A significant valley polarization effect is observed owing to the tunable band gap in K and K' valleys by the off-resonant light. The predicted phenomena open up roots for the development of ultrafast information processing, storage in petahertz-band optoelectronics and valley-resolved transport.