Room-temperature electrical control of polarization and emission angle in a cavity-integrated 2D pulsed LED.

Devices based on two-dimensional (2D) semiconductors hold promise for the realization of compact and versatile on-chip interconnects between electrical and optical signals. Although light emitting diodes (LEDs) are fundamental building blocks for integrated photonics, the fabrication of light sources made of bulk materials on complementary metal-oxide-semiconductor (CMOS) circuits is challenging. While LEDs based on van der Waals heterostructures have been realized, the control of the emission properties necessary for information processing remains limited.

Valley-polarized exciton currents in a van der Waals heterostructure.

Valleytronics is an appealing alternative to conventional charge-based electronics that aims at encoding data in the valley degree of freedom, that is, the information as to which extreme of the conduction or valence band carriers are occupying. The ability to create and control valley currents in solid-state devices could therefore enable new paradigms for information processing. Transition metal dichalcogenides (TMDCs) are a promising platform for valleytronics due to the presence of two inequivalent valleys with spin-valley locking and a direct bandgap, which allows optical initialization and readout of the valley state.

Defect induced, layer-modulated magnetism in ultrathin metallic PtSe.

Defects are ubiquitous in solids and often introduce new properties that are absent in pristine materials. One of the opportunities offered by these crystal imperfections is an extrinsically induced long-range magnetic ordering, a long-time subject of theoretical investigations. Intrinsic, two-dimensional (2D) magnetic materials are attracting increasing attention for their unique properties, which include layer-dependent magnetism and electric field modulation.

Polarization switching and electrical control of interlayer excitons in two-dimensional van der Waals heterostructures.

Long-lived interlayer excitons in van der Waals heterostructures based on transition metal dichalcogenides, together with unique spin-valley physics, make them promising for next-generation photonic and valleytronic devices. While the emission characteristics of interlayer excitons have been studied, efficient manipulation of their valley-state, a necessary requirement for information encoding, is still lacking. Here, we demonstrate comprehensive electrical control of interlayer excitons in a MoSe/WSe heterostructure.

Room-temperature electrical control of exciton flux in a van der Waals heterostructure.

Devices that rely on the manipulation of excitons-bound pairs of electrons and holes-hold great promise for realizing efficient interconnects between optical data transmission and electrical processing systems. Although exciton-based transistor actions have been demonstrated successfully in bulk semiconductor-based coupled quantum wells, the low temperature required for their operation limits their practical application. The recent emergence of two-dimensional semiconductors with large exciton binding energies may lead to excitonic devices and circuits that operate at room temperature.

Optospintronics in Graphene via Proximity Coupling.

The observation of micrometer size spin relaxation makes graphene a promising material for applications in spintronics requiring long-distance spin communication. However, spin dependent scatterings at the contact/graphene interfaces affect the spin injection efficiencies and hence prevent the material from achieving its full potential. While this major issue could be eliminated by nondestructive direct optical spin injection schemes, graphene's intrinsically low spin-orbit coupling strength and optical absorption place an obstacle in their realization.

Suppressing Nucleation in Metal-Organic Chemical Vapor Deposition of MoS Monolayers by Alkali Metal Halides.

Toward the large-area deposition of MoS layers, we employ metal-organic precursors of Mo and S for a facile and reproducible van der Waals epitaxy on c-plane sapphire. Exposing c-sapphire substrates to alkali metal halide salts such as KI or NaCl together with the Mo precursor prior to the start of the growth process results in increasing the lateral dimensions of single crystalline domains by more than 2 orders of magnitude. The MoS grown this way exhibits high crystallinity and optoelectronic quality comparable to single-crystal MoS produced by conventional chemical vapor deposition methods.