Studying the low-entropy Mott transition of bosons in a three-dimensional optical lattice by measuring the full momentum-space density

TL;DR

This study combines experimental measurements and theoretical analysis to investigate the low-entropy Mott transition in 3D optical lattices, revealing critical behavior consistent with the 3D XY universality class through momentum-space density measurements.

Contribution

It demonstrates that momentum distribution measurements can detect critical behavior of the superfluid transition in trapped ultracold bosons, aligning with quantum Monte Carlo predictions.

Findings

Sharp transition in momentum density at critical U/J

Critical behavior matches 3D XY universality class

Momentum tomography reveals superfluid transition traits

Abstract

We report on a combined experimental and theoretical study of the low-entropy Mott transition for interacting bosons trapped in a three-dimensional (3D) cubic lattice -- namely, the interaction-induced superfluid-to-normal phase transition in the vicinity of the zero-temperature Mott transition. Our analysis relies on the measurement of the 3D momentum distribution, which allows us to extract the momentum-space density $\rho({\bf k}={\bf 0})$ at the center of the Brillouin zone. Upon varying the ratio between the interaction $U$ and the tunnelling energy $J$ across the superfluid transition, we observe that $\rho({\bf k}={\bf 0})$ exhibits a sharp transition at a value of $U/J$ consistent with the bulk prediction from quantum Monte Carlo. In addition, the variation of $\rho({\bf k}={\bf 0})$ with $U/J$ exhibits a critical behavior consistent with the expected 3D XY universality class. Our results show that the tomographic reconstruction of the momentum distribution of ultracold bosons can reveal traits of the critical behavior of the superfluid transition even in an inhomogeneous trapped system.