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arXiv:1106.2386 · Physical Review A

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

Nguyen Thanh Phuc, Yuki Kawaguchi, Masahito Ueda

Published Oct 31, 2011• 32 citations
arXivHTMLPDF

Abstract

We investigate the effects of thermal and quantum fluctuations on the phase diagram of a spin-1 ${}^{\text{87}}\text{Rb}$ Bose-Einstein condensate (BEC) under the quadratic Zeeman effect. Due to the large ratio of spin-independent to spin-dependent interactions of ${}^{\text{87}}\text{Rb}$ 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 broken-axisymmetry 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.

DOI
10.1103/physreva.84.043645

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We consider the effect of thermal fluctuations on rotating spinor F=1F=1F=1 condensates in axially symmetric vortex phases, when all the three hyperfine states are populated. We show that the relative phase among different components of the order parameter can fluctuate strongly due to the weakness of the interaction in the spin channel. These fluctuations can be significant even at low temperatures. Fluctuations of relative phase lead to significant fluctuations of the local transverse magnetization of the condensate. We demonstrate that these fluctuations are much more pronounced for the antiferromagnetic state than for the ferromagnetic one.
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