Modification of the Heavy Hole Wave-function in Multiply Occupied Magnetic Quantum Dots*

We compare the magnetic field PL peak energy red shift of ZnTe Quantum Dots (QDs) embedded in a ZnMnSe matrix using two types of laser excitation: (a) Excitation at 405 nm (3.06 eV) with photon energy above the ZnMnSe matrix gap. This leads to electron-hole pair generation mainly in the matrix. (b) Excitation at 488 nm (2.54 eV) with photon energy below the ZnMnSe matrix gap but above the bandgap of the ZnTe QDs. In the latter case, carriers are excited directly into the ZnTe QDs.
The PL peak energy magnetic red shift is up to 3 times larger with 488 nm excitation compared to excitation using 405 nm excitation. Under 488 nm excitation an additional PL feature associated with the e₁l₁shell is observed indicating multiple hole occupancy of the QDs. Using exact diagonalization, we study the doubly occupied quantum dot. We find that in our system, the enhanced exchange interaction between the hole and the Mn ion spins causes the triplet state to be the ground state. Furthermore, the hole-hole repulsion results in the extension of the hole wavefunction further into the ZnMnSe matrix which leads to enhanced magnetic PL red shift.