Controlling the paramagnetic-defects response in mixed-phase layered MoS2 nanosheets with light

Abstract

The paramagnetic response of mixed-phase (1T/2H) layered MoS2 nanosheets’ powder is investigated by means of electron paramagnetic resonance (EPR) in pulse and continuous regime at low temperatures (from 8 to 60 K), with external laser optical excitations. Under dark condition, the sample exhibits two distinct 1/2 spin signals corresponding to different point defects within the semiconducting phase (2H) of MoS2 layers. Spin-echo detection of the two signals demonstrates their potential use for quantum processing at low temperature. Under illumination by optical laser beams, both EPR signal intensities are substantially and simultaneously reduced in a reversible and almost instantaneous manner. The proportion of signals extinction is found to depend on the optical power P and temperature T, while being independent of the optical wavelength remaining above the electronic bandgap, from 405 to 785 nm. The fitting of EPR intensities as functions of P and T based on a simple excitation/relaxation model leads to the prediction of an almost complete and reversible signals extinction at T = 4 K and P = 324 mW, leading to a potential fully optically controlled spin switch. Investigation of the commutation time between dark and illuminated states shows that the mixed-phase (1T/2H) sample displays faster dynamics, as compared to single-phase (2H) samples.