Electronic states of graphene quantum dots induced by nanobubbles

We analyze the effects of the strain-induced pseudo-magnetic fields (PMFs) originating from nanobubbles (NBs) to examine the possibility for a graphene quantum dot (QD) created by strain engineering. We study the electronic structures and quantum transport properties of graphene subjected to an NB, and report that the presence of PMFs facilitates a strong confinement of Dirac fermions. A circular geometry of the NB locally establishes the characteristic PMFs with C-3 symmetry, resulting in threefold localized states according to the given symmetry. We demonstrate the formation of a graphene QD induced by the NB via the conductance resonances calculated through the NB between opposite quantum Hall edge channels. Analyzing the scattering wavefunctions for the resonances, we confirm the existence of ground and excited states in the graphene QD. In addition, we show a possible valley-polarization in the graphene QD, as a consequence of quantum interference between symmetric and anti-symmetric valley-coupled modes.