Fig. 3: Characterization of EL helicity.
a The evolution of EL helicity (bilayer CrI3/hBN/WSe2) under different Vtg, measured under 2 T out-of-plane magnetic field and with Vbias  = 2.5 V. b EL helicity dependence when varying Vbias (after reaching the EL threshold conditions), as measured with 2 T out-of-plane field and Vtg = 1 V. c, d compares the circular polarization of the EL and PL signals at 2 T magnetic field. The PL was measured at a WSe2/CrI3 heterostructure region without hBN barrier, excited by linearly polarized 633 nm laser. The EL spectra were measured in a CrI3/hBN/WSe2 device. EL and PL possess opposite circular polarizations. e The exemplary schematics illustrate the spin-polarized carrier injection process, where the spin polarization results in K valley and σ + EL emission. The solid and dashed arrows indicate the allowed and forbidden carrier injection. B┴ represents the out-of-plane magnetic field. f Under the same CrI3 spin alignment, the interlayer charge transfer favors the quenching of K valley electrons and therefore results in a higher -K exciton population and σ- PL emission.
