Generation and Control of Ultrafast Circular Photon Drag Current in Multilayer PtSe_2 Revealed Via Terahertz Emission

摘要

The generation and control of ultrafast photocurrents on the surface oftransition-metal dichalcogenides (TMDs) are essential for the developmentof advanced optoelectronic devices. A detailed understanding ofthe mechanism of ultrafast photocurrent generation is primarily neededto design functional devices. Here, it is reported that ultrafast photocurrentsin multilayer PtSe_2 are induced by the photon drag effect with highconversion efficiency. Particularly, under circularly polarized laser excitation,anisotropic in-plane photon drag currents are generated, leading tothe elliptically polarized terahertz (THz) radiation directly controlled by thehelicity of the pump beam. Furthermore, a new model called “THz emissionby the circular ac Hall effect” (TECacHE) is proposed to unveil the carriertransport process. It is observed that the origins of elliptically polarizedTHz emission controlled by helicity involve the pure circular photon dragcurrent and the retardation induced by the Lorentz force. Besides, ultrafastternary encoding is proposed and demonstrated by polarized THz emission.The results not only provide a new contactless detection model to studysurface ultrafast photocurrents but also afford a fundamental investigationof the circular photon drag current in layered TMDs for THz telecommunicationdevices.