  We consider a hybrid plasmon-exciton system comprised of a resonant molecular
subsystem and three Au wires supporting a dipole mode which can be coupled to a
dark mode in controllable fashion by variation of a symmetry parameter. The
physics of such a system under strong coupling conditions is examined in
detail. It is shown that if two wires supporting the dark mode are covered with
molecular layers the system exhibits four resonant modes for a strong coupling
regime due to asymmetry and lifted degeneracy of the molecular state in this
case, while upon having molecular aggregates covering the top wire with dipolar
mode, three resonant modes appear. Pump-probe simulations are performed to
scrutinize the quantum dynamics and find possible ways to control
plasmon-exciton materials. It is demonstrated that one can design hybrid
nanomaterials with highly pronounced Fano-type resonances when excited by
femtosecond lasers.
