Manipulation of Valley Pseudospin by Selective Spin Injection in Chiral Two-Dimensional Perovskite/Monolayer Transition Metal Dichalcogenide Heterostructures.

Monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted great interest in spintronics and valleytronics due to the spin-valley locking effect. To efficiently control and manipulate the valley pseudospin is of paramount importance for valley-based electronics and optoelectronics. A variety of strategies have been developed to address the valley pseudospin including optical, electrical, and magnetic methods; nonetheless, they involve either below liquid-nitrogen temperature or an external magnetic field, which increases the cost and complexity of the devices. Here, we report a straightforward way to manipulate valley polarization in monolayer TMDs via selective spin injection in chiral 2D perovskite/monolayer TMD (e.g., MoS2 and WSe2) van der Waals heterostructures without requiring an external magnetic field or specially designed device structures. We show the dangling-bond-free vdW interface can allow an impressive average spin injection efficiency of 78% to produce persistent valley polarization in monolayer MoS2 (WSe2) over 10% from liquid-nitrogen temperature to above 200 K. We attribute the valley polarization of monolayer MoS2 (WSe2) to selective spin injection from chiral 2D perovskites, which can effectively introduce population imbalance between valleys in monolayer MoS2 (WSe2). Our findings provide an alternative strategy to manipulate the valley polarization in TMDs without requiring circularly polarized light excitation, below liquid-nitrogen temperature, or external magnetic field, and thus would promote the development of perovskite-based spintronic and valleytronic devices.