Trapping of Ultracold Atoms in a 10 $\mu $m-Period Permanent Magnetic Lattice

We report the trapping of cold $^{87}$Rb atoms in a 10 $\mu $m-period 1D magnetic lattice constructed from a TbGdFeCo magnetic microstructure on an atom chip. About 3$\times $10$^{5}$ atoms, optically pumped into the $F $=1, $m_{F}$ = \textbf{-}1 ground state to reduce losses due to three body recombination, are loaded into $\sim $100 lattice sites at $\sim $10 $\mu $m below the chip surface with a trap lifetime of $\sim $12 s. Individual clouds in the lattice have been spatially resolved with in-situ absorption imaging. RF spectroscopy measurements at a specific lattice site indicate an atom temperature of 1-2 $\mu $K, close to the calculated BEC transition temperature of 1.5 $\mu $K for 2000 atoms. Besides offering potential technical advantages over optical lattices, and the ability to be mounted on an atom chip [1], magnetic lattices can potentially be tailored to arbitrary geometries such as triangular-based and honeycomb lattices [2]. In future we plan to seek a clear signature of the BEC transition in the multiple lattice traps; study decoherence times for a two-component ultracold gas close to the chip surface using by Ramsey interferometry; and implement a 2D magnetic lattice, with periods down to $\sim $1 $\mu $m and tailored geometries, using state-of-the-art magnetic microstructure technology, with a view to perform quantum tunneling experiments.\\[4pt] [1] M. Singh et al J. Phys. B \textbf{41}, 065301 (2008).\\[0pt] [2] R. Schmied et al \textit{New J. Phys}. \textbf{12}, 103029 (2010).