Dan M. Stamper-Kurn

Observation of Feshbach resonances in a Bose–Einstein condensate

It has long been predicted that the scattering of ultracold atoms can be altered significantly through a so-called ‘Feshbach resonance’. Two such resonances have now been observed in optically trapped Bose–Einstein condensates of sodium atoms by varying an external magnetic field. They gave rise to enhanced inelastic processes and a dispersive variation of the scattering length by a factor of over ten. These resonances open new possibilities for the study and manipulation of Bose–Einstein condensates.

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}

Spontaneous symmetry breaking in a quenched ferromagnetic spinor Bose–Einstein condensate

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

BRAGG SPECTROSCOPY OF A BOSE-EINSTEIN CONDENSATE

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

State-Insensitive Cooling and Trapping of Single Atoms in an Optical Cavity

. 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.

Strongly Enhanced Inelastic Collisions in a Bose-Einstein Condensate near Feshbach Resonances

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.

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

A central goal in condensed matter and modern atomic physics is the exploration of quantum phases of matter—in particular, how the universal characteristics of zero-temperature quantum phase transitions differ from those established for thermal phase transitions at non-zero temperature. Compared to conventional condensed matter systems, atomic gases provide a unique opportunity to explore quantum dynamics far from equilibrium. For example, gaseous spinor Bose–Einstein condensates (whose atoms have non-zero internal angular momentum) are quantum fluids that simultaneously realize superfluidity and magnetism, both of which are associated with symmetry breaking. Here we explore spontaneous symmetry breaking in 87Rb spinor condensates, rapidly quenched across a quantum phase transition to a ferromagnetic state. We observe the formation of spin textures, ferromagnetic domains and domain walls, and demonstrate phase-sensitive in situ detection of spin vortices. The latter are topological defects resulting from the symmetry breaking, containing non-zero spin current but no net mass current.

OBSERVATION OF METASTABLE STATES IN SPINOR BOSE-EINSTEIN CONDENSATES

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.