Thin wire shortening of plasmonic nanoparticle dimers: the reason for red shifts

We studied experimentally and theoretically resonance characteristics of plasmonic nanoparticle dimers connected by a narrow metal wire. The "conductive" coupling between the particles results in complete redistribution of the surface charge yielding abrupt red shift of the plasmon resonance: detuning >900 nm and order of magnitude improvement in intensity enhancement. The resonance in the conductive coupling regime is determined completely by the characteristics of the unified particle and significantly different from that of capacitive coupling.