Multihole edge states in Su-Schrieffer-Heeger chains with interactions

TL;DR

This paper investigates how nearest-neighbor interactions influence topological phases in SSH chains, revealing interaction-induced phase transitions, edge states, and many-body phenomena like hole accumulation at edges.

Contribution

It provides a combined numerical and analytical study of interaction effects on SSH topological phases, including a mapping for two-hole states to non-interacting models.

Findings

Interactions induce phase transitions between topological regimes.

Topological edge states are identified in the equivalent non-interacting model.

Many-body states with holes localized at edges are predicted.

Abstract

We address the effect of nearest-neighbor (NN) interactions on the topological properties of the Su-Schrieffer-Heeger (SSH) chain, with alternating hopping amplitudes t1 and t2. Both numerically and analytically, we show that the presence of interactions induces phase transitions between topologically different regimes. In the particular case of one-hole excitations in a half-filled SSH chain, the V=t2 vs. t1=t2 phase diagram has topological phases at diagonal regions of the phase plane. The interaction acts in this case as a passivation potential. For general filling of the SSH chain, different eigensubspaces of the SSH Hamiltonian may be classified as topologically trivial and non-trivial. The two-hole case is studied in detail in the large interaction limit, and we show that a mapping can be constructed of the two-hole SSH eigensubspaces into one-particle states of a non-interacting one-dimensional (1D) tight-binding model, with interfaces between regions with different hopping constants and local potentials. The presence of topological edge states in the equivalent chain can be readily identifed, as well as their correspondence to the original two-hole states. Furthermore, we found that the presence of the NN interaction generates a state where two holes occupy two consecutive edge states. Such many-body states should also occur for arbitrary filling leading to the possibility of a macroscopic hole gathering at the surface (at consecutive edge states).