Alkali Gases in Optical Lattices: A New Type of Quantum Crystals?

TL;DR

This paper explores the analogy between alkali gases in optical lattices and quantum crystals, proposing a vacancy liquid model that explains phase transitions and impurity behavior with potential for Bose-Einstein condensation.

Contribution

It introduces the vacancy liquid concept as an alternative to Mott transition explanation and discusses impurity dynamics and phase behavior in alkali gases within optical lattices.

Findings

Vacancy liquid can undergo Bose-Einstein condensation at accessible temperatures.

Large vacancy concentrations lead to system decomposition into hyperfine components.

Impurity behavior resembles 3He in superfluid mixtures.

Abstract

Similarities between alkali gases in optical lattices with non-integer occupation of the lattice sites and quantum crystals are explored. The analogy with the vacancy liquid (VL) provides an alternative explanation to the Mott transition for the recent experiment on the phase transition in the lattice. The VL can undergo BEC with T_{c} within experimental reach. Direct and vacancy-assisted mechanisms of the band motion for hyperfine impurities are discussed. Large concentration of vacancies can result in the spatial decomposition of the system into pure hyperfine components. Below the vacancy condensation the impurity component resembles 3He in 3He-HeII mixtures.