Interaction-induced multiparticle bound states in the continuum

TL;DR

This paper predicts a new type of multiparticle bound states in the continuum within an interacting Bose-Hubbard model, demonstrating their properties and potential for Thouless pumping through interaction modulation.

Contribution

It introduces a novel multiparticle BIC analog in many-body quantum systems, linking interaction effects to bound states in the continuum.

Findings

Identification of quasi-BICs as bound pairs in a standing wave

Demonstration of Thouless pumping of quasi-BICs via interaction modulation

Observation of opposite movement of bound pairs relative to the standing wave

Abstract

Bound states in the continuum (BICs) are localized modes residing in the radiation continuum. They were first predicted for single-particle states, and became a general feature of many wave systems. In many-body quantum physics, it is still unclear what would be a close analog of BICs, and whether interparticle interaction may induce BICs. Here, we predict a novel type of multiparticle states in the interaction-modulated Bose-Hubbard model that can be associated with the BIC concept. Under periodic boundary conditions, a so-called quasi-BIC appears as a bound pair residing in a standing wave formed by the third particle. Under open boundary conditions, such a hybrid state becomes an eigenstate of the system. We demonstrate that the Thouless pumping of the quasi-BICs can be realized by modulating the onsite interactions in space and time. Surprisingly, while the center-of-mass of the quasi-BIC is shifted by a unit cell in one cycle, the bound pair moves in the opposite direction with the standing wave.