Enhanced Valley Polarization in WS₂/LaMnO₃ Heterostructure

Abstract

Monolayer transition metal dichalcogenides have attracted great attention for potential applications in valleytronics. However, the valley polarization degree is usually not high because of the intervalley scattering. Here, a largely enhanced valley polarization up to 80% in monolayer WS2 under nonresonant excitation at 4.2 K is demonstrated using WS2/LaMnO3 thin film heterostructure, which is much higher than that for monolayer WS2 on SiO2/Si substrate with a valley polarization of 15%. Furthermore, the greatly enhanced valley polarization can be maintained to a high temperature of about 160 K with a valley polarization of 53%. The temperature dependence of valley polarization is strongly correlated with the thermomagnetic curve of LaMnO3, indicating an exciton–magnon coupling between WS2 and LaMnO3. A simple model is introduced to illustrate the underlying mechanisms. The coupling of WS2 and LaMnO3 is further confirmed with an observation of two interlayer excitons with opposite valley polarizations in the heterostructure, resulting from the spin‐orbit coupling induced splitting of the conduction bands in monolayer transition metal dichalcogenides. The results provide a pathway to control the valleytronic properties of transition metal dichalcogenides by means of ferromagnetic van der Waals engineering, paving a way to practical valleytronic applications.

Electrically and Magnetically Tunable Valley Polarization in Monolayer MoSe2 Proximitized by a 2D Ferromagnetic Semiconductor

“…There can be many reasons that lead to line width broadening, including impurities at the interface, enhanced thermal phonon scattering, and charge transfer. [35,36] But in the case of Cr 2 Ge 2 Te 6 /MoSe 2 heterojunction, the dominant factor for the broadening may be charge transfer. Figure S9 (Supporting Information) presents the spatial correlation of the PL intensity of monolayer MoSe 2 and heterojunction.…”

Thickness-dependent excitonic properties of WSe2/FePS3 van der Waals heterostructures

“…[26][27][28] The construction of van der Waals heterostructure interfaces provides an exciting platform for studying excitonmagnon interaction effects. 29,30 However, most magnetic materials are indirect bandgap semiconductors with very poor luminescence efficiency. Their investigations are mainly focused on magnetic and electronic properties.…”

Dramatically Enhanced Valley‐Polarized Emission by Alloying and Electrical Tuning of Monolayer WTe2xS2(1‐x) Alloys at Room Temperature with 1T′‐WTe2‐Contact

“…[17] Various strategies aiming at enhancing the valley polarization by further breaking the spatial-inversion symmetry have been proposed, including applying magnetic fields, chemical doping of magnetic elements, and employing magnetic proximity effects. [17][18][19][20][21][22] However, with respect to these methods for enhancing the valley polarization, the efficiency of applying an external magnetic field is extremely low for valley polarization (≈0.3 meV per Tesla); magnetic doping suffers from the formation of inhomogeneously distributed dopant clusters; and magnetic proximity effects are easily diminished by the valley submergence. Alternative approaches by electrical and optical control of the valley polarization in TMDs at room temperature and under off-resonance conditions would be more practical and desirable.…”