Nanoscience and Quantum Engineering

We are pursuing research into the electronic and optical properties of a range of nanoscale systems. Most of our work deals with two-dimensional (2D) layered materials, their monolayers, and their heterostructures. We also explore the properties of zero-dimensional quantum dots, and one-dimensional carbon nanotubes, and the paths in which they interact with the 2D materials. We are currently investigating 2D systems that include graphene and various transition metal dichalcogenides, such as MoS2. Our aim is to understand the electronic and optical properties of novel materials of reduced dimensionality and structures composed of these building blocks. Such nanoscale materials differ from bulk materials in various important ways: They experience strong quantum confinement effects that modify the properties of electrons and photons; they interact much more strongly with the external environment through electrostatic, mechanical, and chemical interactions; and they tend to manifest much stronger many-body effects than bulk materials, because of the reduced dielectric screening. These underlying properties and the strong tunability of nanoscale materials render them very intriguing scientifically and endow them with technologically interesting properties.

Our principal approach to the study of such nanoscale materials and structures is through the creative application of a variety of optical spectroscopy techniques, with a spectral range extending from the THz to the UV. Our approaches typically emphasize the ability to probe an individual nanostructure (such as a single 2D layer) or seek to elucidate the ultrafast dynamical process in these materials through femtosecond laser spectroscopy. In exploring the novel properties of such materials and our ability to alter them through electrostatic gating, the dielectric environment, mechanical strain, heterostructure formation, etc., we also consider new applications in photonics, opto-electronics, and valleytronics. Working with our collaborators, we have, for example, developed new designs for optical modulators based on graphene integrated into a photonic crystal cavity. We are exploring the potential role that valley-specific excitations and occupancy could play for electronic and photonic devices. Finally, we are also studying the formation and functioning of quantum emitters in 2D materials.