Linear Dynamic Polarizability and the Absorption Spectrum of an Exciton   in an Aharonov-Bohm Quantum Ring
  We analytically solve the problem of an exciton (with particles interacting by a delta potential) in a one-dimensional quantum ring in the presence of an Aharonov-Bohm flux. By following a more straightforward method than in earlier works we determine the energy spectrum and the associated eigenfunctions together with other physical properties of the system in closed analytical forms. After finding the energy spectra of the exciton in this system, we then calculate the dynamic linear electric polarizability and the absorption coefficients; we find that the magnetic flux changes the values of the absorption coefficients dramatically and that by changing the value of magnetic flux parameter from 0 to 0.5 dark exciton states states transform to bright ones and vice versa. 
A.V. Ghazaryan, A.P.Djotyan, K. Moulopoulos, A.A. Kirakosyan
cond-mat.mes-hall quant-ph