Magnetic field dependence of the dynamics of ⁸⁷Rb spin-2 Bose-Einstein condensates

We experimentally studied the spin-dependent collision dynamics of ⁸⁷Rb spin-2 Bose-Einstein condensates confined in an optical trap. The condensed atoms were initially populated in the ∣F=2,m_F=0⟩ state, and their time evolutions in the trap were measured in the presence of external magnetic field strengths ranging from 0.1 to 3.0 G. The atom loss rate due to inelastic two-body collisions was found to be 1.4(2)×10⁻¹³ cm³ s⁻¹. Spin mixing in the F=2 manifold developed dramatically for the first few tens of milliseconds, and the oscillations in the population distribution between different magnetic components were observed over a limited range of magnetic field strengths. The antiferromagnetic property of this system was deduced from the magnetic field dependence on the evolution of relative populations for each m_F component.