Spinor Bose-Einstein condensates in optical traps

We have studied the equilibrium state of spinor condensates in an optical trap [1]. In contrast to magnetically trapped condensates, spinor condensates have the orientation of the spin as a degree of freedom, which can be described by a multi-component wavefunction (one for each magnetic sublevel). In an F=1 spinor condensate subject to spin relaxation, two mF=0 atoms can collide and produce a mF=1 and a mF=-1 atom and vice versa. The most dramatic effect was seen when we started with a condensate in a pure mF=0 state. Depending on the external magnetic field, the formation of three domains of mF = +1, 0, -1 atoms was observed. The figure shows a sequence of images with different dwell times in the optical trap. Starting with either the pure mF=0 component (upper series) or with a 50-50 mixture of the mF= ±1 components (lower series), the same equilibrium distribution was reached. Comparison of such equilibrium distributions to a theoretical model revealed that the spin-dependent interaction c " F 1 ⋅ " F 2 between two sodium atoms in the F=1 state is antiferromagnetic (i.e. c>0). Furthermore, the experimental results showed clear evidence for the miscibility of mF = -1 and mF = +1 components and the immiscibility of mF = ±1 and mF = 0. This opens the possibility for detailed studies of miscible and immiscible multicomponent condensates.