Metastable spin-phase diagrams in antiferromagnetic Bose-Einstein condensates

TL;DR

This paper theoretically investigates the metastable spin-phase diagram of antiferromagnetic spin-1 Bose-Einstein condensates at various temperatures, explaining experimental observations and predicting temperature-induced shifts in phase boundaries.

Contribution

It introduces a non-selfconsistent Hartree-Fock approach to analyze metastable states and phase boundaries in spinor BECs, revealing temperature effects on phase transitions.

Findings

Metastable states occur near phase boundaries in spinor BECs.

Temperature shifts the ferromagnetic-polar transition boundary.

Results align with recent experimental observations.

Abstract

Spinor Bose-Einstein condensates under external magnetic fields exhibit well-characterized spin domains of its ground state due to spin-dependent interactions. At low temperatures, collision-induced spin-mixing instabilities may promote the condensate to dwell into metastable states occurring near the phase boundaries. In this work, we study theoretically the metastable spin-phase diagram of a spin-1 antiferromagnetic Bose-Einstein condensate at zero and finite temperatures. The approach makes use of Hartree-Fock theory and exploits the symmetry of the Hamiltonian and of the order parameters yielding a closed system of transcendental equations for the free energy, fully avoiding the use of selfconsistency. Our results are consistent with recent experiments and allow us to explain qualitatively the different types of observed quench dynamics. In addition, we found that similar phenomena should occur in antiferromagnetic spinor condensates with a sudden change in the temperature. It is shown also that the increase of temperature induces a traceable shift of the Ferromagnetic-Polar transition boundary, behavior previously not noticed by selfconsistent mean-field calculations.