Striped Ferronematic ground states in a spin-orbit coupled $S=1$ Bose gas

TL;DR

This paper theoretically maps the phase diagram of a spin-orbit coupled spin-1 Bose gas, revealing novel stripe ferronematic states and phase transitions driven by interactions, Raman coupling, and Zeeman effects.

Contribution

It introduces the first mean-field phase diagram showing stripe ferronematic phases in spin-orbit coupled spin-1 Bose gases, highlighting the interplay of interactions and external fields.

Findings

Identification of stripe XY ferromagnetic phases for attractive interactions.

Discovery of biaxial ferronematic phases with oscillating density and spin.

Analysis of phase stability under quadratic Zeeman shifts.

Abstract

We theoretically establish the mean-field phase diagram of a homogeneous spin-$1$, spin-orbit coupled Bose gas as a function of the spin-dependent interaction parameter, the Raman coupling strength and the quadratic Zeeman shift. We find that the interplay between spin-orbit coupling and spin-dependent interactions leads to the occurrence of ferromagnetic or ferronematic phases which also break translational symmetry. For weak Raman coupling, increasing attractive spin-dependent interactions (as in $^{87}$Rb or $^7$Li) induces a transition from a uniform to a stripe XY ferromagnet (with no nematic order). For repulsive spin-dependent interactions however (as in $^{23}$Na), we find a transition from an $XY$ spin spiral phase ($<S_{z} >= 0$ and uniform total density) with uniaxial nematic order, to a biaxial ferronematic, where the total density, spin vector and nematic director oscillate in real space. We investigate the stability of these phases against the quadratic Zeeman effect, which generally tends to favor uniform phases with either ferromagnetic or nematic order but not both. We discuss the relevance of our results to ongoing experiments on spin-orbit coupled, spinor Bose gases.