Higher-order acoustic phonon oscillations in Au nanoparticles controlled by a sequence of ultrashort strain pulses generated by superdiffusive hot electrons

摘要

We demonstrate that higher-order acoustic phonon oscillations of self-assembled Au nanoparticles can be excited using higher frequency bandwidth picosecond acoustic pulses generated by superdiffusive hot electrons. These modes require directional excitations such as a longitudinal strain pulse, being inaccessible in a direct optical excitation scheme. They are detected using the periodic shift of the surface plasmon resonance and are coherently controlled by a sequence of delayed acoustic pulses. Acoustic mode calculations show that the high-frequency mode corresponds to two higher-order spheroidal modes.