Fate of Bosonic Topological Edge Modes in the Presence of Many-Body Interactions

TL;DR

This paper demonstrates that bosonic topological edge modes can persist in a quantum ladder model despite many-body interactions, using tensor network methods to reveal their signatures in experimentally accessible correlations.

Contribution

It provides evidence that many-body interactions do not necessarily destroy bosonic topological edge modes, challenging previous assumptions based on non-interacting theories.

Findings

Bosonic edge modes persist with full many-body interactions.

Edge mode signatures are detectable in dynamical structure factors.

The study maps the topological phase diagram and identifies fractionalized excitations.

Abstract

Many magnetic materials are predicted to exhibit bosonic topological edge modes in their excitation spectra, because of the nontrivial topology of their magnon, triplon, or other quasi-particle band structures. However, there is a discrepancy between theory prediction and experimental observation, which suggests some underlying mechanism that intrinsically suppresses the expected experimental signatures, like the thermal Hall current. Many-body interactions that are not accounted for in the non-interacting quasi-particle picture are most often identified as the reason for the absence of the topological edge modes. Here we report persistent bosonic edge modes at the boundaries of a ladder quantum paramagnet with gapped triplon excitations in the presence of the full many-body interaction. We use tensor network methods to resolve topological edge modes in the time-dependent spin-spin correlations and the dynamical structure factor, which is directly accessible experimentally. We further show that signatures of these edge modes survive even when the non-interacting quasi-particle theory breaks down, discuss the topological phase diagram of the model, demonstrate the fractionalization of its low-lying excitations, and propose potential material candidates.