Single-photon scattering and bound states in a one-dimensional waveguide with a topological giant atom

We investigate the single-photon scattering and bound states in a coupled resonator waveguide (CRW) which couples to a topological giant atom (TGA) via two distant sites. Here, the TGA is constructed by a one-dimensional Su-Schrieffer-Heeger chain with a finite length. By modulating the topological phase of the TGA, the incident photon in the CRW can be completely reflected or transmitted, and is therefore beneficial to designing a coherent photonic device. Meanwhile, we also achieve two pairs of bound states locating respectively above and below the continuum. Whether the gap is open or closed depends on the boundary condition of the TGA. Therefore, the combination of topology and interference provides us with an exciting opportunity to manipulate the photonic state in the context of waveguide quantum electrodynamics.