Wideband tunable infrared topological plasmon polaritons in dimerized chains of doped-silicon nanoparticles.

We investigate the topological plasmon polaritons (TPPs) in one-dimensional dimerized doped silicon nanoparticle chains, as an analogy of the topological edge states in the Su–Schrieffer–Heeger model. The photonic band structures are analytically calculated by taking all near-field and far-field dipole–dipole interactions into account. For longitudinal modes, it is demonstrated that the band topology can be well characterized by the complex Zak phase irrespective of the lattice constant and doping concentration. By numerically solving the eigenmodes of a finite system, it is found that a dimerized chain with a nonzero complex Zak phase supports nontrivial topological eigenmodes localized over both edges. By changing the doping concentration of Si, it is possible to tune the resonance frequency of the TPPs from far-infrared to near-infrared, and the localization lengths of the edge modes are also modulated accordingly. In addition, it is shown that a higher working temperature can lead to significantly smaller decay rates. Since these TPPs are highly protected modes that can achieve a strong confinement of electromagnetic waves and are also immune to impurities and disorder, they can provide a potentially tunable tool for robust and enhanced light–matter interactions in the infrared spectrum. [ABSTRACT FROM AUTHOR]