Quantum Monte Carlo study of the visibility of one-dimensional Bose-Fermi mixtures

TL;DR

This paper uses quantum Monte Carlo simulations to study the visibility of bosons in one-dimensional Bose-Fermi mixtures, resolving discrepancies between previous theory and experiments by identifying parameter regimes and phenomena affecting visibility.

Contribution

It provides new QMC simulation results that clarify the behavior of bosonic visibility in 1D mixtures, including effects of fermion admixture and molecule formation.

Findings

Identification of parameter regimes with reduced and increased bosonic visibility

Observation of kinks in visibility linked to domain evolution

Prediction of structure from boson-fermion molecule formation

Abstract

The study of ultracold optically trapped atoms has opened new vistas in the physics of correlated quantum systems. Much attention has now turned to mixtures of bosonic and fermionic atoms. A central puzzle is the disagreement between the experimental observation of a reduced bosonic visibility ${\cal V}_b$, and quantum Monte Carlo (QMC) calculations which show ${\cal V}_b$ increasing. In this paper, we present QMC simulations which evaluate the density profiles and ${\cal V}_b$ of mixtures of bosons and fermions in one-dimensional optical lattices. We resolve the discrepancy between theory and experiment by identifying parameter regimes where ${\cal V}_b$ is reduced, and where it is increased. We present a simple qualitative picture of the different response to the fermion admixture in terms of the superfluid and Mott-insulating domains before and after the fermions are included. Finally, we show that ${\cal V}_b$ exhibits kinks which are tied to the domain evolution present in the pure case, and also additional structure arising from the formation of boson-fermion molecules, a prediction for future experiments.