Quantum Critical Point in Strongly Correlated $^{87}$Rb Atoms in Optical Lattice

TL;DR

This paper introduces a Bosonic variational method to analyze strongly correlated $^{87}$Rb atoms in optical lattices, identifying a quantum critical point and phase diagram with implications for superfluid-insulator transitions.

Contribution

The paper proposes a novel Bosonic projected variational approach to study strongly correlated lattice bosons and maps out the phase diagram including the quantum critical point.

Findings

Identification of two characteristic lattice depths for $^{87}$Rb atoms.

Prediction of suppressed superfluid state near the superfluid-insulator transition.

Determination of the quantum critical point at $V=12.3E_r$.

Abstract

In this paper, the Bosonic projected variational method is proposed to study the strongly correlated $^{87}{\rm Rb}$ atoms in optical lattice. A global phase diagram is obtained by this method. There exist two characteristic lattice depths $V$ for $^{87}{\rm Rb}$ atoms in optical lattice : one is $% V=9.5E_r$ to label the maximum height of the 'zero-momentum' peak of condensation, the other is the quantum critical point for the superfluid-insulator (SI) transition at $V=12.3E_r$. As a result of strongly correlated effect for lattice Bosons, the suppressed superfluid state is predicted near the SI transition with the suppressed superfluid density and the very slowly velocity of the sound-like excitons.