Spin and excitation energy transfer in a quantum-dot pair system through optical near-field interactions

We discuss the mechanism of the spin and excitation energy transfer in a quantum-dot pair system driven by optical near fields (ONFs). When one of the pair is excited either by an ONF or effectively by a far field, the energy and spin information of the induced exciton can be transferred to the other quantum dot via a near-field optical interaction. Moreover, it is possible to flip the electron spin during the transfer process, depending on the resonant state of the energy levels of the quantum dots. We present the electron-spin selection rules, and calculate the spin and excitation energy transfer rates between the quantum-dot pair and the spin polarization, in terms of the exciton-polariton basis for ONFs. A way of making experimental observations is also suggested.