Finite Temperature Phase Transition in a Cross-Dimensional Triangular Lattice

TL;DR

This study experimentally investigates the finite-temperature superfluid transition of bosonic atoms in a versatile 3D triangular lattice, revealing deviations from mean field theory in reduced dimensions and highlighting strong many-body correlations.

Contribution

First experimental characterization of superfluid transition across a dimension-crossover triangular lattice, demonstrating deviations from mean field predictions in lower dimensions.

Findings

Finite temperature superfluid transition matches mean field in 3D.

Deviations increase as the system approaches lower dimensions.

Strong many-body correlations are observed beyond mean field theory.

Abstract

Atomic many-body phase transitions and quantum criticality have recently attracted much attention in non-standard optical lattices. Here we perform an experimental study of finite-temperature superfluid transition of bosonic atoms confined in a three dimensional triangular lattice, whose structure can be continuously deformed to dimensional crossover regions including quasi-one and two dimensions. This non-standard lattice system provides a versatile platform to investigate many-body correlated phases. For the three dimensional case, we find that the finite temperature superfluid transition agrees quantitatively with the Gutzwiller mean field theory prediction, whereas tuning towards reduced dimensional cases, both quantum and thermal fluctuation effects are more dramatic, and the experimental measurement for the critical point becomes strongly deviated from the mean field theory. We characterize the fluctuation effects in the whole dimension crossover process. Our experimental results imply strong many-body correlations in the system beyond mean field description, paving a way to study quantum criticality near Mott-superfluid transition in finite temperature dimension-crossover lattices.