Dynamics of $F=2$ Spinor Bose-Einstein Condensates

We experimentally investigate and analyze the rich dynamics in $F=2$ spinor Bose-Einstein condensates of ${}^{87}\mathrm{R}\mathrm{b}$. An interplay between mean-field driven spin dynamics and hyperfine-changing losses in addition to interactions with the thermal component is observed. In particular, we measure conversion rates in the range of ${10}^{-12}{\mathrm{c}\mathrm{m}}^3{\mathrm{s}}^{-1}$ for spin-changing collisions within the $F=2$ manifold and spin-dependent loss rates in the range of ${10}^{-13}{\mathrm{c}\mathrm{m}}^3{\mathrm{s}}^{-1}$ for hyperfine-changing collisions. We observe polar behavior in the $F=2$ ground state of ${}^{87}\mathrm{R}\mathrm{b}$, while we find the $F=1$ ground state to be ferromagnetic. We further see a magnetization for condensates prepared with nonzero total spin.

Figure 1

Time-dependent observation of different $m_F$ components starting from the initially prepared states denoted by (a)–(d). Shown are spinor condensates separated by a Stern-Gerlach method (time of flight 31 ms).

Figure 2

Spin dynamics and spin-dependent losses. (a) Relative population of the $m_F$ states of a condensate initially prepared in $|0⟩$. (b) Thermalization of a BEC in the $|+2⟩$ state from initially $|0⟩+|+1⟩$. (c) Total spin of the condensate initially prepared in $|+1⟩$. (d) Decay curves for total number of condensed atoms in all $m_F$ states, given for different initial $m_F$ preparations.