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

Abstract

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 <i>via</i> selective spin injection in chiral 2D perovskite/monolayer TMD (<i>e</i>.<i>g</i>., 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.