Magnetic proximity effect in ultrathin freestanding WS2/LaMnO3 van der Waals heterostructures

Abstract

With complex coupling of multiple degrees of freedom, transition metal oxides (TMOs) provide a promising platform to tune the magnetic property in heterostructures via the magnetic proximity effect. Recent realization of freestanding TMO thin films allows further extension of this technique to novel two-dimensional heterostructures by mechanically stacking with van der Waals materials. Here, we demonstrate the presence of significant magnetic exchange interactions in a heterostructure of 8 nm freestanding LaMnO3 and monolayer WS2. The high magnetization in freestanding LaMnO3 leads to valley degeneracy breaking in WS2, resulting in unbalanced valley polarization in the photoluminescence (PL). Further temperature-dependent PL measurements reveal the same transition behavior as the magnetization in the freestanding LaMnO3 film. Our results unlock new approaches for tuning the magnetism and the valley degree of freedom in ultrathin two-dimensional heterostructures.