Effects of thermal and quantum fluctuations on the phase diagram of a spin-1 87Rb Bose-Einstein condensate

TL;DR

This paper explores how thermal and quantum fluctuations influence the phase diagram of a spin-1 87Rb Bose-Einstein condensate, revealing temperature-dependent magnetization and quantum depletion effects.

Contribution

It provides new insights into the impact of fluctuations on phase transitions and magnetization in spinor BECs, especially considering the large spin-independent to spin-dependent interaction ratio.

Findings

Condensate and magnetization emerge at different temperatures in the broken-axisymmetry phase.

Magnetized condensate induces spin coherence among noncondensed atoms, affecting temperature-dependent magnetization.

Quantum fluctuations significantly alter the ground-state phase diagram at zero temperature.

Abstract

We investigate effects of thermal and quantum fluctuations on the phase diagram of a spin-1 87Rb Bose-Einstein condensate (BEC) under a quadratic Zeeman effect. Due to the large ratio of spinindependent to spin-dependent interactions of 87Rb atoms, the effect of noncondensed atoms on the condensate is much more significant than that in scalar BECs. We find that the condensate and spontaneous magnetization emerge at different temperatures when the ground state is in the brokenaxisymmetry phase. In this phase, a magnetized condensate induces spin coherence of noncondensed atoms in different magnetic sublevels, resulting in temperature-dependent magnetization of the noncondensate. We also examine the effect of quantum fluctuations on the order parameter at absolute zero, and find that the ground-state phase diagram is significantly altered by quantum depletion.