Two-body physics in the Su-Schrieffer-Heeger model

TL;DR

This paper explores two interacting bosons in the SSH lattice, revealing novel edge bound states, bulk-boundary correspondence breaking, and proposing an optical fiber setup for experimental simulation of these phenomena.

Contribution

It introduces the existence of edge bound states under conditions where single-particle states do not, and proposes a realistic optical fiber experiment to simulate two-body SSH physics.

Findings

Edge bound states exist even without single-particle edge states.

Bulk-boundary correspondence breaks at large interactions.

Optical fiber setup can simulate and observe these phenomena.

Abstract

We consider two interacting bosons in a dimerized Su-Schrieffer-Heeger (SSH) lattice. We identify a rich variety of two-body states. In particular, for open boundary conditions and moderate interactions, edge bound states (EBS) are present even for the dimerization that does not sustain single-particle edge states. Moreover, for large values of the interactions, we find a breaking of the standard bulk-boundary correspondence. Based on the mapping of two interacting particles in one dimension onto a single particle in two dimensions, we propose an experimentally realistic coupled optical fibers setup as quantum simulator of the two-body SSH model. This setup is able to highlight the localization properties of the states as well as the presence of a resonant scattering mechanism provided by a bound state that crosses the scattering continuum, revealing the closed-channel population in real time and real space.