Anderson localization of composite particles

TL;DR

This paper explores how the coupling between internal and translational degrees of freedom in composite quantum particles affects their localization in disordered systems, revealing that entanglement weakens localization.

Contribution

It demonstrates that internal-translation coupling and entanglement significantly influence localization, with numerical evidence from two-particle and rotor models showing dramatic effects.

Findings

Entanglement weakens localization in composite particles.

Coupling impacts localization even with few internal states.

Numerical simulations confirm the effect in 1D and 2D lattices.

Abstract

We investigate the effect of coupling between translational and internal degrees of freedom of composite quantum particles on their localization in a random potential. We show that entanglement between the two degrees of freedom weakens localization due to the upper bound imposed on the inverse participation ratio by purity of a quantum state. We perform numerical calculations for a two-particle system bound by a harmonic force in a 1D disordered lattice and a rigid rotor in a 2D disordered lattice. We illustrate that the coupling has a dramatic effect on localization properties, even with a small number of internal states participating in quantum dynamics.