based van der Waals heterostructures*

Defects in semiconductors and dielectrics can provide rich physics with technological potential such as quantum photon emission, spin control and they might be potential platforms for realizing quantum entanglement. In transition metal dichalcogenides, defects have been found to play important role as they affect the doping and the spin-valley relaxation dynamics. Herein we study localized states in WS₂ by means of tunnelling spectroscopy using van der Waals heterostructures of h-BN/graphene/WS₂/metal. The monolayer graphene electrodes provide for weak screening of electric-fields, which allows us to tune the chemical potential of WS₂ with the back-gate. The obtained conductance maps as a function of bias and gate voltage reveal single-electron transistor behaviour (Coulomb blockade) with a rich set of transport features like excited states and negative differential resistance regimes. Moreover, by applying a perpendicular magnetic field, we study the spin ground- and excited states of single defects.