Coherent-phonon-assisted excitation transfer via optical near fields in dilute magnetic semiconductor nanostructures

Optical near-field (ONF) phenomena observed in nanoscale systems have been applied to nano-fabrication and nano-photoelectronic devices for the last decade. Excitation transfer (ET) is an elementary process caused by ONF interaction localized at the nanoscale in real space. Recently, we have observed spin-dependent ET controlled by an external field and discovered the sign of assistance of phonons. In this work, we elucidate that the assistance of coherent phonons in ET originates from two types of mechanism: energy resonance between exciton levels renormalized by phonon effects and enhancement by phase matching between coherent oscillation of populations and phonon oscillation. This study will stimulate the development of the application of ET via a ONF to nano-photoelectronic devices.