Circular photogalvanic effect in 2D van der Waals heterostructure

Abstract: Utilizing spin or valley degree of freedom is one of the promising approaches to realize more energy-efficient information processing. In the 2D transition metal dichalcogenide, the spin/valley current can be generated by utilizing the circular photogalvanic effect (CPGE), i.e., the generation of photocurrent by a circularly polarized light. Here we show that an in-plane electric field at MoS2/WSe2 heterostructure-electrode boundary results in an electrically tunable circular photogalvanic effect (CPGE) under optical excitation with normal incidence. The observed CPGE can be explained by the valence band shift due to the in-plane electric field and different effective relaxation times between hole and electron combined with the valley optical selection rule. Furthermore, we show that the CPGE can be controlled by changing the Fermi level using an out-of-plane electric field. Such phenomena persist even at room temperature. This finding may facilitate the utilization of 2D heterostructure as an opto-valleytronics and opto-spintronics device platform.