Light-induced enhanced torque on double-V-type quantum emitters via quantum interference in spontaneous emission

Abstract

We consider interaction of a pair of counterpropagating spatially inhomogeneous weak vortex beams with a quantum emitter that has a double-V level scheme and closely situated upper levels. We show that in such a situation a quantized torque is exerted on the emitter, which is directly proportional to the topological charge of the vortices and is strongly influenced and even enhanced by the quantum interference of spontaneous emission from the doublet. Depending on the particular initial states of the emitter, absorption, optical transparency, or lasing without inversion can be realized. The interference in spontaneous emission can be modified when the double-V emitter is situated above the surface of a thick slab of Bi2Te3 and the vortex beams propagate parallel to the surface. The light-induced torque rotates the emitters generating a persistent toroidal current flow above the bismuth-chalcogenide surface, whose intensity is remotely controlled by the distance from the surface.