Strongly Interacting Two-Dimensional Bose Gases

TL;DR

This study investigates strongly interacting two-dimensional Bose gases across various regimes, measuring thermodynamic properties and comparing them with theoretical models, revealing significant deviations from mean-field predictions at strong interactions.

Contribution

It provides experimental measurements of thermodynamic quantities in 2D Bose gases over a wide interaction range and compares results with advanced theoretical calculations.

Findings

Coupling constants decrease significantly at strong interactions.

Thermodynamic quantities exhibit logarithmic dependence on interaction strength.

Experimental results align with extended classical-field and renormalization theories.

Abstract

We prepare and study strongly interacting two-dimensional Bose gases in the superfluid, the classical Berezinskii-Kosterlitz-Thouless (BKT) transition, and the vacuum-to-superfluid quantum critical regimes. A wide range of the two-body interaction strength 0.05 < g < 3 is covered by tuning the scattering length and by loading the sample into an optical lattice. Based on the equations of state measurements, we extract the coupling constants as well as critical thermodynamic quantities in different regimes. In the superfluid and the BKT transition regimes, the extracted coupling constants show significant down-shifts from the mean-field and perturbation calculations when g approaches or exceeds one. In the BKT and the quantum critical regimes, all measured thermodynamic quantities show logarithmic dependence on the interaction strength, a tendency confirmed by the extended classical-field and renormalization calculations.