Quantum localization and bound state formation in Bose-Einstein condensates

TL;DR

This paper explores how ultracold bosonic atoms in optical lattices can exhibit exponential quantum localization in the absence of disorder, driven by the interplay of nonlinearity and energy spectrum bounds.

Contribution

It demonstrates the occurrence of exponential localization in the maximally excited state and identifies conditions and experimental schemes for observing this phenomenon.

Findings

Localization occurs in the maximally excited state of the lowest energy band.

Conditions for neglecting upper energy bands are established.

Experimental detection via visibility measurements is proposed.

Abstract

We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity and a bounded energy spectrum.