Neutral and positively charged excitons in quantum ring

We study theoretically quantized states of the neutral and positively charged exciton complexes confined within a circular narrow ring in the presence of the magnetic field applied along the symmetry axis. We show that in the structural adiabatic limit, when the width of the pattern of the particles pathways within the ring is much smaller than its radius, the wave equations for both complexes are separable and their exact solutions can be found in a form of the Fourier series of one and two variables, respectively. We present results of calculation of the lower energies of complexes as functions of the ring's radius and the magnetic field strength for different values of the electron-to-hole mass ratio. We found that in the molecular adiabatic limit, when this ratio tends to zero and the model describes the corresponding donor complexes, the physical interpretation of the quantum-size effect and the oscillations of energy levels in threading magnetic field revealed for the excitons spectra becomes more transparent. (C) 2013 Elsevier B.V. All rights reserved.