  Tunable plasmonic resonances across the visible and near infrared spectra
have provided novel ways to develop next-generation nanophotonic devices. In
this study, by using optothermally controllable phase-changing material (PCM),
we successfully induced highly tunable charge transfer plasmon (CTP) resonance
modes. To this end, we have designed a two-member dimer assembly including gold
cores and Ge2Sb2Te5 (GST) shells in distant, touching, and overlapping
conditions. We successfully demonstrated that toggling between amorphous
(dielectric) and crystalline (conductive) phases of GST allows for achieving
tunable dipolar and CTP resonances along the near-infrared spectrum. The
proposed dimer structures can help forming optothermally controlled devices
without further geometrical variations in the geometry of the design, and
having strong potential for advanced plasmon modulation and fast data routing.
