BEC-on-a-chip goes wireless
In August 2006 we have demonstrated BEC in 87Rb on a permanent magnet atom chip. The chip consists of a piece of magnetized FePt foil, cut into an "F"-like shape. It is in-plane magnetized and designed to produce a self-biasing Ioffe-Pritchard trap that would persist in the absence of any external magnetic fields. Atoms from a mirror MOT are transported into the FePt trap by applying uniform external magnetic fields. Once the atoms have been loaded we switch off all power supplies.
The condensation occurs after forced RF evaporation at about Tc = 1.1 µK with 6000 atoms. Further evaporation leaves us with a pure condensate of about 1500 atoms. The measured trap frequencies are 130 Hz (axial) and 5.5 kHz (radial). The first unambiguous observation was on Thu. 17 August 2006.
Due to the permanent magnetization we cannot switch the trap off to do free-space expansion. Instead we launch the atoms away from the surface and image them after expansion in a region of low field gradient. Additional diagnostics are obtained by RF spectroscopy.
Researchers: René Gerritsma, Thomas Fernholz, Iuliana Barb, Shannon Whitlock, Robert Spreeuw.
The chip was fabricated by Yu Tao Xing, in collaboration with the group of Jeroen Goedkoop.
More information about our work on magnetic-film atom chips.