  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 (SSH) 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. Moreover, 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 length of the
edge modes are also modulated accordingly. 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 light-matter
interaction in the infrared spectrum.
