Title: Giant excitonic magneto-optical Faraday rotation in single semimagnetic CdTe/Cd_{1-x}Mn_{x}Te quantum ring

Abstract: Magnetic tuning of the bound exciton states and corresponding giant Zeeman splitting (GZS) between {\sigma}^{+} and {\sigma}^{-} excitonic transitions in CdTe/Cd_{1-x}Mn_{x}Te quantum ring has been investigated in the Faraday configuration for various concentrations of Mn^{2+} ions, using the variational technique in the effective mass approximation. The sp-d exchange interaction between the localized magnetic impurity ions and the delocalized charge carriers has been accounted via mean-field theory with the inclusion of a modified Brillouin function. The enhancement of the GZS, and in turn, the effective g-factor with the application of an external magnetic field, is strikingly manifested in type-I - type-II transition in the band structure, which has been well explained by computing the overlap integral between the electron and hole, and the in-plane exciton radius. This highlights the extraordinary magneto-optical properties, including the giant Faraday rotation and associated Verdet constant, which have been calculated using single oscillator model. The oscillator strength and exciton lifetime have been estimated, and are found to be larger than in the bulk diluted magnetic semiconductors (DMS) and quantum wells, reflecting stronger confinement inside the quantum ring. The results show that the DMS-based quantum ring exhibits more extensive Zeeman splitting, which gives rise to ultra-high Verdet constant of 2.6 \times 10^{9}rad/Tesla/m, which are a few orders of magnitude larger than in the existing quantum systems and magneto-optical materials.