Topologically bound states, non-Hermitian skin effect and flat bands, induced by two-particle interaction

TL;DR

This paper explores how two-particle interactions in a one-dimensional lattice induce topologically nontrivial states, including bound and edge states, driven by the non-Hermitian skin effect and resulting in flat bands.

Contribution

It reveals the emergence of interaction-induced topological bound and edge states, coupling center-of-mass and relative motions in a non-Hermitian setting.

Findings

Interaction drives nontrivial two-particle states

Non-Hermitian skin effect localizes states

Formation of flat bands due to interactions

Abstract

We study theoretically quantum states of two repelling spinless particles in a one-dimensional tight-binding model with simple periodic lattice and open boundary conditions. We demonstrate, that when the particles are not identical, their interaction drives nontrivial correlated two-particle states, such as bound states, edge states as well as interaction-induced flat bands. Specifically, the center-of-mass and relative motions of two particles become coupled in a topologically nontrivial way. By virtue of the non-Hermitian skin effect the localization of the center of mass enforces the localization of the relative motion and formation of the bound states.