Near-field-induced optical force on a metal particle and C60: Real-time and real-space electron dynamics simulation

Takeshi Iwasa and Katsuyuki Nobusada

Optical forces induced by a near field are calculated for a 1-mm-sized metal particle mimicked by a jellium model and for C60 in the framework of real-time and real-space time-dependent density-functional theory combined with a nonuniform light-matter interaction formalism, fully taking account of multipole interaction. A highly localized near field nonuniformly polarizes these molecules. The locally induced polarization charges in the molecules are partly canceled by the screening charges. The polarization and screening charges generally contribute to the attractive and repulsive forces, respectively, and a sensible balance between these charges results in several peaks in the optical force as a function of the frequency of the near field. The resonance excitation does not necessarily maximally induce the net force, and the force exerted on the molecules strongly depends on the details of their electronic structures. The optical force is larger in the metal particle than in C60. We also found that the optical force depends linearly on the intensity of the near field.

DOI