Quantum field theory of nematic transitions in spin orbit coupled spin-1 polar bosons

TL;DR

This paper provides an analytical study of quantum phase transitions in a one-dimensional ultra-cold spin-1 polar boson gas with spin-orbit coupling, revealing distinct nematic phases and critical behaviors relevant to experiments.

Contribution

It introduces a low-energy analytical solution for the phase diagram of spin-1 polar bosons with spin-orbit coupling, identifying new nematic and spin-disordered phases and their transition mechanisms.

Findings

Identified two nematic superfluid phases depending on quadratic Zeeman field sign.

Discovered a spin-disordered superfluid phase at strong coupling.

Characterized the nature of phase transitions, including BKT and Ising criticality.

Abstract

We theoretically study an ultra-cold gas of spin-1 polar bosons in a one dimensional continuum which are subject to linear and quadratic Zeeman fields and a Raman induced spin-orbit coupling. Concentrating on the regime in which the background fields can be treated perturbatively we analytically solve the model in its low-energy sector, i.e. we characterize the relevant phases and the quantum phase transitions between them. Depending on the sign of the effective quadratic Zeeman field $\epsilon$, two superfluid phases with distinct nematic order appear. In addition, we uncover a spin-disordered superfluid phase at strong coupling. We employ a combination of renormalization group calculations and duality transformations to access the nature of the phase transitions. At $\epsilon = 0$, a line of spin-charge separated pairs of Luttinger liquids divides the two nematic phases and the transition to the spin disordered state at strong coupling is of the Berezinskii-Kosterlitz-Thouless type. In contrast, at $\epsilon \neq 0$, the quantum critical theory separating nematic and strong coupling spin disordered phases contains a Luttinger liquid in the charge sector that is coupled to a Majorana fermion in the spin sector (i.e. the critical theory at finite $\epsilon$ maps to a quantum critical Ising model that is coupled to the charge Luttinger liquid). Due to an emergent Lorentz symmetry, both have the same, logarithmically diverging velocity. We discuss the experimental signatures of our findings that are relevant to ongoing experiments in ultra-cold atomic gases of $^{23}$Na.