A. P. Chikkatur

Realization of Bose-Einstein condensates in lower dimensions.

Bose-Einstein condensates of sodium atoms have been prepared in optical and magnetic traps in which the energy-level spacing in one or two dimensions exceeds the interaction energy between atoms, realizing condensates of lower dimensionality. The crossover into two-dimensional and one-dimensional condensates was observed by a change in aspect ratio and by the release energy converging to a nonzero value when the number of trapped atoms was reduced.

Spin domains in ground-state Bose–Einstein condensates

Bose–Einstein condensates — a low-temperature form of matter in which a macroscopic population of bosons occupies the quantum-mechanical ground state — have been demonstrated for weakly interacting, dilute gases of alkali-metal and hydrogen atoms. Magnetic traps are usually employed to confine the condensates, but have the drawback that spin flips in the atoms lead to untrapped states. For this reason, the spin orientation of the trapped alkali atoms cannot be regarded as a degree of freedom. Such condensates are therefore described by a scalar order parameter, like the spinless superfluid 4He. In contrast, a recently realized optical trap for sodium condensates confines atoms independently of their spin orientations. This offers the possibility of studying ‘spinor’ condensates in which spin comprises a degree of freedom, so that the order parameter is a vector rather than scalar quantity. Here we report the observation of equilibrium states of sodium spinor condensates in an optical trap. The freedom of spin orientation leads to the formation of spin domains in an external magnetic field, which can be either miscible or immiscible with one another.

Optical Confinement of a Bose-Einstein Condensate

Bose-Einstein condensates of sodium atoms have been confined in an optical dipole trap using a single focused infrared laser beam. This eliminates the restrictions of magnetic traps for further studies of atom lasers and Bose-Einstein condensates. More than five million condensed atoms were transferred into the optical trap. Densities of up to

Spin domains in ground state spinor Bose-Einstein condensates

3 \times 10^{15} cm^{-3}

BRAGG SPECTROSCOPY OF A BOSE-EINSTEIN CONDENSATE

of Bose condensed atoms were obtained, allowing for a measurement of the three-body decay rate constant for sodium condensates as

Excitation of Phonons in a Bose-Einstein Condensate by Light Scattering

K_3 = (1.1 \pm 0.3) \times 10^{-30} cm^6 s^{-1}

OBSERVATION OF METASTABLE STATES IN SPINOR BOSE-EINSTEIN CONDENSATES

. At lower densities, the observed 1/e lifetime was more than 10 sec. Simultaneous confinement of Bose-Einstein condensates in several hyperfine states was demonstrated.

Observation of Vortex Phase Singularities in Bose-Einstein Condensates

Bose–Einstein condensates — a low-temperature form of matter in which a macroscopic population of bosons occupies the quantum-mechanical ground state — have been demonstrated for weakly interacting, dilute gases of alkali-metal and hydrogen atoms. Magnetic traps are usually employed to confine the condensates, but have the drawback that spin flips in the atoms lead to untrapped states. For this reason, the spin orientation of the trapped alkali atoms cannot be regarded as a degree of freedom. Such condensates are therefore described by a scalar order parameter, like the spinless superfluid 4He. In contrast, a recently realized optical trap for sodium condensates confines atoms independently of their spin orientations. This offers the possibility of studying ‘spinor’ condensates in which spin comprises a degree of freedom, so that the order parameter is a vector rather than scalar quantity. Here we report the observation of equilibrium states of sodium spinor condensates in an optical trap. The freedom of spin orientation leads to the formation of spin domains in an external magnetic field, which can be either miscible or immiscible with one another.

Observation of Superfluid Flow in a Bose-Einstein Condensed Gas

Properties of a Bose-Einstein condensate were studied by stimulated, two-photon Bragg scattering. The high momentum and energy resolution of this method allowed a spectroscopic measurement of the mean-field energy and of the intrinsic momentum uncertainty of the condensate. The coherence length of the condensate was shown to be equal to its size. Bragg spectroscopy can be used to determine the dynamic structure factor over a wide range of energy and momentum transfers.

Propagation of bose-einstein condensates in a magnetic waveguide

thereby “optically imprinting” phonons into the gas. The momentum imparted to the condensate was measured by a time-of-flight analysis. This study is the first to explore phonons with wavelengths much smaller than the size of the trapped sample, allowing a direct connection to the theory of the homogeneous Bose gas. We show the excitation of phonons to be significantly weaker than that of free particles, providing dramatic evidence for correlated momentum excitations in the many-body condensate wave function. In optical Bragg spectroscopy, an atomic sample is illuminated by two laser beams with wave vectors k1 and k2 and a frequency difference v which is much smaller than their detuning D from an atomic resonance. The intersecting beams create a periodic, traveling intensity