Correlated metallic two particle bound states in quasiperiodic chains

TL;DR

This paper investigates how two interacting particles in a quasiperiodic chain transition between localized and delocalized states, revealing a correlated metallic phase caused by resonant mixing of eigenstates.

Contribution

It demonstrates the existence of a correlated metallic phase for two particles in a quasiperiodic chain, driven by nonperturbative interaction effects, expanding understanding of many-body localization phenomena.

Findings

Two-particle states become delocalized at finite interaction strength.

At larger interactions, states localize again, indicating a non-monotonic transition.

Correlated metal states enable coherent particle movement across the chain.

Abstract

Single particle states in a chain with quasiperiodic potential show a metal-insulator transition upon the change of the potential strength. We consider two particles with local interaction in the single particle insulating regime. The two particle states change from being localized to delocalized upon an increase of the interaction strength to a nonperturbative finite value. At even larger interaction strength the states become localized again. This transition of two particle bound states into a correlated metal is due to a resonant mixing of the noninteracting two particle eigenstates. In the discovered correlated metal states two particles move coherently together through the whole chain, therefore contributing to a finite conductivity.