Gate-controlled spin relaxation in bulk WSe2 flakes

We have studied the spin relaxation dynamics in both n- and p-type layered bulk WSe2 under a perpendicular electric field by employing time-resolved Kerr rotation and helicity-resolved transient reflection measurements. The experimental results reveal the efficient tuning of spin relaxation time from 3 ps to 46 ps by the external electric field at 10 K. The dependence of spin relaxation time on the external electric field is understood based on active interlayer hopping. These studies demonstrate the gate-tunable spin polarization and relaxation in bulk transition metal dichalcogenides (TMDCs), which are fundamentally important for understanding spin dynamics and the practical design of spintronic devices based on bulk TMDCs.