Author: Tony F Heinz
Requested Type: Pre-Selected Invited
Submitted: 2015-03-17 06:21:13
348 Via Pueblo Mall
Stanford, CA 94305
Graphene has attracted attention worldwide because of its exceptional potential for novel science and technology. Recently, this interest has expanded to the much wider class of 2D materials that occur as layers of van-der-Waals crystals that exhibit weak interlayer coupling, but strong in-plane bonding. While preserving graphene’s flexibility and tunability by external perturbations, this broader set of materials provides access to more varied electronic and optical properties.
Here we review our understanding of the properties of atomically thin layers of semiconductors in the family of transition metal dichalcogenides, MX2 where M = Mo, W and X = S, Se, Te. In the limit of atomically thin layers, these materials exhibit a transition from optically dark indirect-gap semiconductor to bright direct-gap materials. The 2D layers display r strong many-body interactions, with exciton binding energies of 100’s of meV and stable charged excitons at room temperature. These materials also provide new possibilities for control of the valley character of charge carriers. In particular, the helicity of light allows the selection of one of the degenerate, but distinct K and K’ valleys in the Brillouin zone. We will discuss these emergent properties, as well as new possibilities that arise by forming tailored heterostructures.