Trapping ultracold atoms in a sub-micron-period triangular magnetic lattice

Abstract

We report the trapping of ultracold $^{87}\mathrm{Rb}$ atoms in a 0.7-$\ensuremath{\mu}\text{m}$-period two-dimensional triangular magnetic lattice on an atom chip. The magnetic lattice is created by a lithographically patterned magnetic Co/Pd multilayer film plus bias fields. Rubidium atoms in the $|F=1,{m}_{F}=\ensuremath{-}1\ensuremath{\rangle}$ low-field seeking state are trapped at estimated distances down to about $100\phantom{\rule{0.28em}{0ex}}\mathrm{nm}$ from the chip surface and with calculated mean trapping frequencies up to about $800\phantom{\rule{0.28em}{0ex}}\mathrm{kHz}$. The measured lifetimes of the atoms trapped in the magnetic lattice are in the range 0.4--$1.7\phantom{\rule{0.28em}{0ex}}\mathrm{ms}$, depending on distance from the chip surface. Model calculations suggest the trap lifetimes are currently limited mainly by losses due to one-dimensional thermal evaporation following loading of the atoms from the $Z$-wire trap into the very tight magnetic lattice traps, rather than by fundamental loss processes such as surface interactions, three-body recombination, or spin flips due to Johnson magnetic noise. The trapping of atoms in a $0.7\text{\ensuremath{-}}\ensuremath{\mu}\mathrm{m}$-period magnetic lattice represents a significant step toward using magnetic lattices for quantum tunneling experiments and to simulate condensed matter and many-body phenomena in nontrivial lattice geometries.