Experimental Realization of Degenerate Fermi Gases of ⁸⁷Sr Atoms with 10 or Two Spin Components

We report the experimental realization of quantum degenerate Fermi gases of ⁸⁷Sr atoms under controlled 10- and dual-nuclear-spin configurations. Based on laser cooling and evaporative cooling, we achieve an ultracold Fermi gas of 10⁵ atoms equally distributed over 10 spin states, with a temperature of T/T_F=0.21. We further prepare a dual-spin gas by optically pumping atoms to the m_F=9/2 and m_F=7/2 states and observe a slightly lower T/T_F than that for a 10-spin gas under the same trapping condition, showing efficient evaporative cooling under a decreasing number $N$ of spin states ( $N\ge 2$ ) despite the increasing importance of Pauli exclusion. Given that rethermalization becomes less efficient with $N$ approaching unity, we evaporatively cool an almost polarized gas to 130 nK. The simple and efficient preparation of ultracold Fermi gases of ⁸⁷Sr with tunable spin configurations provides a first step towards engineering topological quantum systems. (paper)