Valley filtering and valley valves in irradiated pristine graphene

We theoretically investigate valley filtering in pristine graphene under irradiation by a bicircular counterrotating laser field. We find that the relative phase between the two counterrotating fields controls quasienergy states and Floquet band occupations in the valleys, enabling highly efficient valley-selective currents and transport responses via an all-optical approach. Varying the relative phase allows us to block contributions from one valley while enabling currents from the opposite valley. For experimental realization, we propose a valley valve configuration involving two graphene nanoribbons irradiated by bicircular counterrotating laser drives with a relative phase shift. Our findings remain robust against moderate disorder and modest changes in laser parameters, enabling the way for practical light-based valleytronics devices.