Tuning of exciton states in a magnetic quantum ring

• The effect of spin interactions on exciton states in a quantum ring is considered.
• Quantum ring containing a single magnetic impurity is studied.
• Multiband approximation has been used for calculation of the exciton states.
• The bright exciton state can be changed to the dark state and vice versa.
• An experimental method is proposed to estimate spin interaction constants.

The exciton states in a CdTe quantum ring subjected to an external magnetic field containing a single magnetic impurity are investigated. We have used the multiband approximation which includes the heavy hole–light hole coupling effects. The electron–hole spin interactions and the s, p–d interactions between the electron, the hole and the magnetic impurity are also included. The exciton energy levels and optical transitions are evaluated using the exact diagonalization scheme. We show that due to the spin interactions it is possible to change the bright exciton state into the dark state and vice versa with the help of a magnetic field. We propose a new route to experimentally estimate the s, p–d spin interaction constants.