Trapping ultracold atoms at 100 nm from a chip surface in a 0.7-micrometer-period magnetic lattice

We report the trapping of ultracold 87Rb atoms in a 0.7 micron-period 2D 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, mF=-1 low-field seeking state are trapped at estimated distances down to about 100 nm from the chip surface and with calculated mean trapping frequencies as high as 800 kHz. The measured lifetimes of the atoms trapped in the magnetic lattice are in the range 0.4 - 1.7 ms, depending on distance from the chip surface. Model calculations suggest the trap lifetimes are currently limited mainly by losses due to surface-induced 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 micrometer-period magnetic lattice represents a significant step towards using magnetic lattices for quantum tunneling experiments and to simulate condensed matter and many-body phenomena in nontrivial lattice geometries.Comment: 11 pages, 7 figure

Radiofrequency spectroscopy of a linear array of Bose-Einstein condensates in a magnetic lattice

We report site-resolved radiofrequency spectroscopy measurements of Bose-Einstein condensates of 87Rb atoms in about 100 sites of a one-dimensional 10 micron-period magnetic lattice produced by a grooved magnetic film plus bias fields. Site-to-site variations of the trap bottom, atom temperature, condensate fraction and chemical potential indicate that the magnetic lattice is remarkably uniform, with variations in trap bottoms of only +/- 0.4 mG. At the lowest trap frequencies (radial and axial frequencies 1.5 kHz and 260 Hz, respectively), temperatures down to 0.16 microkelvin are achieved in the magnetic lattice and at the smallest trap depths (50 kHz) condensate fractions up to 80% are observed. With increasing radial trap frequency (up to 20 kHz, or aspect ratio up to about 80) large condensate fractions persist and the highly elongated clouds approach the quasi-1D Bose gas regime. The temperature estimated from analysis of the spectra is found to increase by a factor of about five which may be due to suppression of rethermalising collisions in the quasi-1D Bose gas. Measurements for different holding times in the lattice indicate a decay of the atom number with a half-life of about 0.9 s due to three-body losses and the appearance of a high temperature (about 1.5 microkelvin) component which is attributed to atoms that have acquired energy through collisions with energetic three-body decay products

Bose-Einstein condensation in a magnetic lattice

This thesis reports the realization of Bose-Einstein condensation (BEC) of 87Rb F=1 atoms in multiple sites of a one-dimensional 10 μm-periods magnetic lattice. The magnetic microtraps are created by a perpendicularly magnetized, multi-layered structure of TbGdFeCo film integrated on to an atom chip, together with uniform bias magnetic fields. Clear signatures for the onset of quantum degeneracy in multiple sites of the the magnetic lattice are provided by in-situ site-resolved radio-frequency spectroscop

Magnetic lattices for ultracold atoms and degenerate quantum gases

We review recent developments in the use of magnetic lattices as a complementary tool to optical lattices for trapping periodic arrays of ultracold atoms and degenerate quantum gases. Recent advances include the realisation of Bose-Einstein condensation in multiple sites of a magnetic lattice of one-dimensional microtraps, the trapping of ultracold atoms in square and triangular magnetic lattices, and the fabrication of magnetic lattice structures with sub-micron period suitable for quantum tunnelling experiments. Finally, we describe a proposal to utilise long-range interacting Rydberg atoms in a large spacing magnetic lattice to create interactions between atoms on neighbouring sites