Molecular states in graphene double quantum dots

We present a double quantum dot structure based on an armchair graphene nanoribbon with three serial narrow constrictions. With appropriate geometry and size, each region in between two constrictions behaves as a tunneling quantum dot. Within the low energy range around the Dirac point, conductance of the structure shows strong resonances. The paired resonance peaks are related to the quasibound molecular states in the tunnel-coupled dots. The quasibound states and the interdot coupling can be effectively tuned by only the geometrical parameters of the structure.