EventBrian D. Gerardot

Quantum dots in two-dimensional heterostructures

Van der Waals (vdW) heterostructures, in which a wide range of unique atomic layers can easily be combined, offer novel prospects to engineer and manipulate quantum confined states. Here I will present two approaches to this exciting prospect. I will first present Coulomb blockade in a vdW quantum dot device with tunnel coupling to a tunable Fermionic reservoir. Hybrid excitons, composed of localized quantum dot states (in WSe2) and Fermi reservoir continuum states (in graphene), are observed due to ultra-strong spin-conserving tunnel coupling resulting from an atomically thin tunnel barrier (hBN). Secondly, I will present spin-layer locking of interlayer valley excitons (IX) trapped in moiré potentials. In a heterostructure of bilayer 2H-MoSe2 and monolayer WSe2, we observe two IX species trapped in moiré potentials with distinct spin-layer-valley configurations. Due to the phenomenon of locked electron spin and layer pseudospin in bilayer 2H-MoSe2, the IX species exhibit opposite valley magnetic moments. Further, we find the 2H-MoSe2 stacking intrinsically locks the atomic registries of IXH and IXR together. Finally, we will discuss photon antibunching of moiré trapped excitons to unambiguously prove their quantum nature.

Brian D. Gerardot

Left figure: A cartoon of “quantum tunnelling” of electrons (red balls with arrows) between a sheet of graphene (top layer, black atoms) and tungsten diselenide (bottom layer, dark and light blue atoms).

Right figure: An illustration of the moiré superlattice formed in a “twisted” MoSe2/WSe2 heterobilayer.

About The Speaker


Professor Gerardot leads the Quantum Photonics Lab at Heriot-Watt University in Edinburgh, Scotland (more information: http://qpl.eps.hw.ac.uk/). His research, at the interface of quantum optics, condensed-matter physics, and materials science, aims to engineer and controllably manipulate quantum states in semiconductor devices, with a particular recent interest in exploring novel van der Waals heterostructure quantum devices.