Quantum fluctuation-induced uniaxial and biaxial spin nematics

TL;DR

This paper demonstrates that quantum fluctuations remove degeneracy in spin nematic phases of hyperfine spin 2 cold atoms, revealing two distinct ground states with higher symmetries and a first-order phase transition.

Contribution

It shows that zero point quantum fluctuations lift degeneracy, leading to uniaxial and biaxial spin nematic ground states with higher symmetries in hyperfine spin 2 cold atoms.

Findings

Zero point quantum fluctuations lift degeneracy in mean field spin nematics.

Two distinct ground states: uniaxial and biaxial spin nematics.

A first order quantum phase transition between the two phases.

Abstract

It is shown that zero point quantum fluctuations (ZPQFs) completely lift the accidental continuous degeneracy that is found in mean field analysis of quantum spin nematic phases of hyperfine spin 2 cold atoms. The result is two distinct ground states which have higher symmetries: a uniaxial spin nematic and a biaxial spin nematic with dihedral symmetry ${Dih}_4$. There is a novel first order quantum phase transition between the two phases as atomic scattering lengths are varied. We find that the ground state of $^{87}Rb$ atoms should be a uniaxial spin nematic. We note that the energy barrier between the phases could be observable in dynamical experiments.