Event

A pair of electrons and holes across the interface of semiconductor heterostructure can form a bound quantum state of the interlayer exciton. In a coupled interface between atomically thin van der Waals layers (vdW), the Coulomb interaction of the interlayer exciton increases further. In this presentation, we will discuss observing interlayer exciton formation in semiconducting transition metal dichalcogenide (TMDC) layers. Unlike conventional semiconductor heterostructures, charge transport in the devices is critically dependent on the interlayer charge transport, electron-hole recombination process mediated by tunneling across the interface. We demonstrate the enhanced electronic, optoelectronic performances in the vdW heterostructures, tuned by applying gate voltages, suggesting that these few atom thick interfaces may provide a fundamental platform to realize novel physical phenomena. I will discuss our effort to realize coherent exciton condensation in TMD heterostructures. In the second part of the presentation, we will discuss magneto-exciton condensation in double-layer graphene systems. In this electronic double layer subject to strong magnetic fields, filled Landau states in one layer bind with empty states of the other layer to form an exciton condensate. Driving current in one graphene layer generates a near-quantized Hall voltage in the other layer, resulting in coherent exciton transport. In our experiment, capitalizing strong Coulomb interaction across the atomically thin hBN separation layer, we realize a superfluid condensation of magnetic-field-induced excitons. Complete experimental control of density, displacement, and magnetic fields in our graphene double-layer system enables us to explore the rich phase diagram of several superfluid exciton phases with the different internal quantum degrees of freedom.