Electron and Electromagnetic Field Dynamics in Nanostructures

We have developed theoretical methods to calculate photoinduced electron dynamics in nanostructured materials such as nanoparticles, quantum-dot arrays, and adsorbate-surface systems. Specifically, we have developed generalized theory of a light-matter interaction beyond a dipole approximation on the basis of the multipolar Hamiltonian with the aim of understanding the near-field excitation of molecules at the 1 nm scale. We have also studied exciton–polariton transmission in quantum dot waveguides. Furthermore, collectivity of plasmonic excitations in small sodium clusters was investigated in depth. Ultrafast relaxation dynamics of a gold cluster and adsorbate dynamics have been elucidated in collaboration with experimental groups.