Far-infrared absorption of vertically coupled self-assembled quantum rings

We investigate theoretically the far-infrared absorption of two vertically coupled quantum rings. The obtained spectrum can be described as a superimposition of inter-ring (bonding-antibonding) and intraring transitions. The two kinds of resonances have different responses to external magnetic fields, depend on different structural parameters and can be switched on and off independently by using polarized light. Structural information on the coupled quantum rings can be obtained by monitoring the magnetoabsorption spectrum of the bonding-antibonding transitions. We also show that direct imaging of the electron energy structure in a single quantum ring is possible by measuring the absorption spectrum of the ring vertically coupled to a quantum dot of similar volume.