Observation of Correlated Particle-Hole Pairs and String Order in Low-Dimensional Mott Insulators

TL;DR

This paper reports the direct detection of correlated particle-hole pairs and string order in one-dimensional bosonic Mott insulators using high-resolution imaging, revealing hidden non-local quantum correlations.

Contribution

It provides the first direct observation of particle-hole pairs and string order in low-dimensional Mott insulators with single-site resolution.

Findings

Detection of correlated particle-hole pairs

Observation of string order in 1D systems

Confirmation of non-local quantum correlations

Abstract

Quantum phases of matter are characterized by the underlying correlations of the many-body system. Although this is typically captured by a local order parameter, it has been shown that a broad class of many-body systems possesses a hidden non-local order. In the case of bosonic Mott insulators, the ground state properties are governed by quantum fluctuations in the form of correlated particle-hole pairs that lead to the emergence of a non-local string order in one dimension. Using high-resolution imaging of low-dimensional quantum gases in an optical lattice, we directly detect these pairs with single-site and single-particle sensitivity and observe string order in the one-dimensional case.