Simulations of ultracold bosonic atoms in optical lattices with anharmonic traps

TL;DR

This study uses quantum Monte Carlo simulations to analyze how anharmonic traps, specifically quadratic and quartic, influence quantum criticality in ultracold bosonic atoms within optical lattices, highlighting the potential for improved experimental observation.

Contribution

It demonstrates that quartic traps enhance local critical fluctuations at the trap center, offering better conditions for observing quantum criticality compared to quadratic traps.

Findings

Quartic traps show similar behavior to quadratic traps but with increased critical fluctuations at the center.

Quantum critical behavior is suppressed in quadratic traps due to potential gradients.

Quartic traps can facilitate the experimental detection of quantum criticality in ultracold bosonic systems.

Abstract

We report results of quantum Monte Carlo simulations in the canonical and the grand-canonical ensemble of the two- and three-dimensional Bose-Hubbard model with quadratic and quartic confining potentials. The quantum criticality of the superfluid-Mott insulator transition is investigated both on the boundary layer separating the two coexisting phases and at the center of the traps where the Mott-insulating phase is first established. Recent simulations of systems in quadratic traps have shown that the transition is not in the critical regime due to the finite gradient of the confining potential and that critical fluctuations are suppressed. In addition, it has been shown that quantum critical behavior is recovered in flat confining potentials as they approach the uniform regime. Our results show that quartic traps display a behavior similar to quadratic ones, yet locally at the center of the traps the bulk transition has enhanced critical fluctuations in comparison to the quadratic case. Therefore quartic traps provide a better prerequisite for the experimental observation of true quantum criticality of ultracold bosonic atoms in optical lattices.