Spin Coupling between Cold Atoms and the Thermal Fluctuations of a Metal Surface

We describe an experiment in which Bose-Einstein condensates and cold atom clouds are held by a microscopic magnetic trap near a room-temperature metal wire $500\mu \mathrm{m}$ in diameter. The lifetime for atoms to remain in the microtrap is measured over a range of distances down to $27\mu \mathrm{m}$ from the surface of the metal. We observe the loss of atoms from the microtrap due to spin flips. These are induced by radio-frequency thermal fluctuations of the magnetic field near the surface, as predicted but not previously observed.