Gated quantum structures in monolayer WSe₂

The family of semiconducting 2H-phase group-VI transition metal dichalcogenides (TMDs) have been suggested to be promising candidates for the development of quantum devices due to their desirable optical and electrical properties. In this talk, we present our work based on gated quantum structures fabricated in encapsulated monolayer tungsten diselenide (WSe₂) with the goal of furthering our understanding of the material and of fabricating functional devices for quantum technologies. More specifically, we concentrate on three important gated quantum structures: quantum dots, a charge detector, and a long one-dimensional channel.

We first present the fabrication of the devices used in this work and demonstrate that high quality contacts are achievable. We then demonstrate that our gate architecture allows us to identify and control quantum dots that have formed in the local minima of electrostatic potential fluctuations in the WSe₂ sheet. Coulomb blockade peaks and diamonds are observed which allow us to extract information about the dot diameter and its charging energy¹. Using this gate architecture, we also demonstrate that a nanoconstriction defined in the monolayer WSe_2­ flake can be used as a charge detector for nearby quantum dots with sensitivities comparable to that of other charge detectors based on graphene². Finally, we present transport measurements related to a gate-defined 1D channel in monolayer WSe₂. In the quasi-ballistic regime of our high mobility sample, we report conductance quantization steps in units of e²/h that remain constant for a large range of applied magnetic fields, indicating the lifting of the spin and valley degeneracies in this system³.

These results bring us closer to achieving functional quantum devices based on electrostatic confinement in semiconducting TMDs and improve our understanding of their electronic properties.