The properties of surface plasmon-polariton (SPP) resonance modes were investigated in a
branched silver nanorod consisting of two nanorods using high energy resolution electron
energy-loss spectroscopy (EELS) combined with scanning transmission electron
microscopy. The experimental EELS maps of the SPP excitation showed a specific
distribution depending on the resonance mode. The analytical formulas of the EELS signal
and the resonance conditions for SPP resonance in the branched nanorod were derived by …