Enhanced valley polarization in WSe₂/YIG heterostructures via interfacial magnetic exchange effect

Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics. Monolayer transition metal dichalcogenides (TMDs) with broken space-inversion symmetry exhibit emerging valley pseudospins, making them ideal platforms for studying valley electronics. However, intervalley scattering of different energy valleys limits the achievable degree of valley polarization. Here, we constructed WSe₂/yttrium iron garnet (YIG) heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%, significantly higher than that of a monolayer WSe₂ on SiO₂/Si (11%). Additionally, multiple sharp exciton peaks appear in the WSe₂/YIG heterostructures due to the strong magnetic proximity effect at the magnetic–substrate interface that enhances exciton emission efficiency. Moreover, under the effect of external magnetic field, the magnetic direction of the magnetic substrate enhances valley polarization, further demonstrating that the magnetic proximity effect regulates valley polarization. Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.