Quantum interference-induced stability of repulsively bound pairs of excitations

TL;DR

This paper investigates the stability of repulsively bound pairs of excitations in quantum systems, revealing that destructive quantum interference significantly suppresses their decay, thus explaining their persistent stability.

Contribution

It demonstrates that quantum interference effects lead to the stability of repulsively bound pairs in Bose-Hubbard and Heisenberg spin chains, a novel insight into their dynamics.

Findings

Bound pairs are stable despite strong repulsive interactions.

Destructive quantum interference suppresses decay transitions.

Stability persists against defect scattering and pair collisions.

Abstract

We study the dynamics of two types of pairs of excitations which are bound despite their strong repulsive interaction. One corresponds to doubly occupied sites in one-dimensional Bose-Hubbard systems, the so-called doublons. The other is pairs of neighboring excited spins in anisotropic Heisenberg spin-1/2 chains. We investigate the possibility of decay of the bound pairs due to resonant scattering by a defect or due to collisions of the pairs. We find that the amplitudes of the corresponding transitions are very small. This is a result of destructive quantum interference and explains the stability of the bound pairs.