Large g factor in bilayer WS2 flakes

Abstract

The valley of transition metal dichalcogenides provides an additional platform to manipulate spin due to its unique selection rule. Normally, intralayer optical transitions in the magnetic field show a Zeeman splitting with a g factor of about -4. Here, we report a remarkable valley Zeeman effect exhibited by the splitting of excitonic emission in a bilayer WS2, with a value of g factor as large as -16.5. The observed large g factor results from the interlayer recombination, as the conduction band and the valence band are modified in opposite directions by the magnetic field in different layers. The interlayer recombination is due to the defect induced inversion symmetry breaking, which is theoretically not accessible in ideal bilayer WS2 with inversion symmetry. The large g factor of interlayer emission offers potential benefits for future optical spin control and detection.