Strong bonding magnetic plasmon hybridizations in double split-ring resonators.

The complex magnetic dipole plasmon couplings in double split-ring resonators are investigated. Two split peaks in the absorption spectrum of these coupled systems are observed, but even the shorter-wavelength resonance peak can be redshifted compared to the peaks of individual rings. The magnetic plasmon fields outside rings are found to play an important role in these strong couplings. Because of them, both bonding and antibonding plasmon hybridizations occur at each split peak. When bonding coupling effects are stronger than those of antibonding ones, this abnormal splitting behavior appears. When the coupling between rings becomes weaker, the splitting phenomenon tends to be normal.