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Van der Waals materials with long-range magnetic order show a range of correlated phenomena that could be of use in the development of optoelectronic and spintronic applications. Magnetically ordered van der Waals semiconductors with spin-polarized currents are, in particular, sensitive to external stimuli such as strain, electrostatic fields, magnetic fields and electromagnetic radiation. Their combination of two-dimensional magnetic order, semiconducting band structure and weak dielectric screening means that these materials could be used to create novel atomically thin opto-spintronic devices. Here we explore the development of van der Waals opto-spintronics. We examine the interplay between optical, magnetic and electronic excitations in van der Waals magnetic semiconductors, and explore the control of their magnetization via external stimuli. We consider fabrication and passivation strategies for the practical handling and design of opto-spintronic devices. We also explore potential opto-spintronic device architectures and applications, which include magnonics, quantum transduction, neuromorphic computing and non-volatile memory. 

Mixed-dimensional van der Waals heterojunctions involve interfacing materials with different dimensionalities, such as a 2D transition metal dichalcogenide and a 0D organic semiconductor. These heterojunctions have shown unique interfacial properties not found in either individual component. Here, we use femtosecond transient absorption to reveal photoinduced charge transfer and interlayer exciton formation in a mixed-dimensional type-II heterojunction between monolayer MoS2 and vanadyl phthalocyanine (VOPc). Selective excitation of the MoS2 exciton leads to hole transfer from the MoS2 valence band to VOPc highest occupied molecular orbit in ∼710 fs. On the contrary, selective photoexcitation of the VOPc layer leads to instantaneous electron transfer from its excited state to the conduction band of MoS2 in less than 100 fs. This light-initiated ultrafast separation of electrons and holes across the heterojunction interface leads to the formation of an interlayer exciton. These interlayer excitons formed across the interface lead to longer-lived charge-separated states of up to 2.5 ns, longer than in each individual layer of this heterojunction. Thus, the longer charge-separated state along with ultrafast charge transfer times provide promising results for photovoltaic and optoelectronic device applications.