Abstract
Adsorbed atoms (adatoms) coupled to the matrix of solid state host materials as impurities can significantly modify their properties. Especially in low-dimensional materials, such as one-dimensional organic polymer chains or quasi-one-dimensional graphene nanoribbons, intriguing manipulation of the optical properties, such as the absorption cross section, is possible. The most widely used approach to couple quantum emitters to optical antennas is based on the Purcell effect. This formalism, however, does not comprise charge transfer from the emitter to the antenna, but only spontaneous emission of the quantum emitter into the tailored photonic environment, that is evoked by the antenna. To capture such effects, we present a tight-binding formalism to couple an adatom to a finite Su-Schrieffer-Heeger chain, where the former is treated as a two-level system and the latter acts as an optical antenna. We systematically analyze how the coupling strength and the position of the adatom influence the optical properties of the molecular chains in the model. We take into account charge transfer from the adatom to the antenna and vice versa via an inter-system hopping parameter, and also include Coulomb interaction within the antenna as well as between the adatom and the antenna. We show that coupling the adatom to one of the bulk atoms of the linear chain results in a substantial change in optical properties already for comparatively small coupling strengths. We also find that the position of the adatom crucially determines if and how the optical properties of the chains are altered. Therefore, we identify this adatom-chain hybrid system as a tunable platform for light-matter interaction at the nanoscale.
Highlights
The Su-Schrieffer-Heeger (SSH) model constitutes a simple yet powerful and instructive tight-binding (TB) based model to describe the electronic and topological properties of solids, and induced a large body of literature within the last four decades [1,2,3,4,5,6,7,8,9,10,11,12,13]
We present a tight-binding formalism to couple an adatom to a finite Su-Schrieffer-Heeger chain, where the former is treated as a two-level system and the latter acts as an optical antenna
We assume the hybrid system to consist of two components: a nanoscopic SSH chain that acts as an optical antenna and an adatom which is effectively described as a two-level system (TLS)
Summary
The Su-Schrieffer-Heeger (SSH) model constitutes a simple yet powerful and instructive tight-binding (TB) based model to describe the electronic and topological properties of solids, and induced a large body of literature within the last four decades [1,2,3,4,5,6,7,8,9,10,11,12,13]. Besides being a playground to explore topological phases [6, 14] and quasiparticles [1, 15,16,17], it is capable of revealing transport properties of organic polymers such as polyacetylene [18] and the electronic energy level diagrams of molecular chains, for instance, if applied to finite systems. It is to a large extent analytically solvable and, allows for powerful conceptual insights into the underlying physical principles.
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