Spin liquid phases of Mott insulating ultracold bosons

TL;DR

This paper explores how tuning interactions in ultracold bosonic gases can induce quantum spin liquid phases, using mean field theory to analyze the relationship between spin, interactions, and magnetic phases.

Contribution

It introduces a mean field theoretical framework for understanding spin liquid phases in Mott insulators of ultracold bosons with large spin, highlighting conditions for realizing s-RVB spin liquids.

Findings

Large-spin bosons with tuned interactions can host spin liquid phases.

Short-range resonating valence bond (s-RVB) phase identified for hyperfine spin > 2.

Tuning scattering lengths influences magnetic phase transitions.

Abstract

Mott insulating ultracold gases posses a unique whole-atom exchange interaction which enables large quantum fluctuations between the Zeeman sublevels of each atom. By strengthening this interaction---either through the use of large-spin atoms, or by tuning the particle-particle interactions via optical Feshbach resonance---one may enhance fluctuations and facilitate the appearance of the long sought-after quantum spin liquid phase---all in the highly tunable environment of cold atoms. To illustrate the relationship between the spin magnitude, interaction strength, and resulting magnetic phases, we present and solve a mean field theory for bosons optically confined to the one particle-per-site Mott state, using both analytic and numerical methods. We find on a square lattice with bosons of hyperfine spin $f>2$, that making the repulsive s-wave scattering length through the singlet channel small---relative to the higher-order scattering channels---accesses a short-range resonating valence bond (s-RVB) spin liquid phase.