Size effects on excitons in nano-rings

The size effects on an exciton in a nano-ring are investigated theoretically by using an effective-mass Hamiltonian which can be separated into terms in centre-of-mass and relative coordinates. The binding energy and oscillator strength of the ground state are calculated for two different ring radii as functions of the ring width. The resulting linear optical susceptibility of the low-lying exciton states is also discussed.