262 research outputs found
Experimental studies of equilibrium vortex properties in a Bose-condensed gas
We characterize several equilibrium vortex effects in a rotating
Bose-Einstein condensate. Specifically we attempt precision measurements of
vortex lattice spacing and the vortex core size over a range of condensate
densities and rotation rates. These measurements are supplemented by numerical
simulations, and both experimental and numerical data are compared to theory
predictions of Sheehy and Radzihovsky [17] (cond-mat/0402637) and Baym and
Pethick [25] (cond-mat/0308325). Finally, we study the effect of the
centrifugal weakening of the trapping spring constants on the critical
temperature for quantum degeneracy and the effects of finite temperature on
vortex contrast.Comment: Fixed minor notational inconsistencies in figures. 12 pages, 8
figure
Observation of Vortex Pinning in Bose-Einstein Condensates
We report the observation of vortex pinning in rotating gaseous Bose-Einstein
condensates (BEC). The vortices are pinned to columnar pinning sites created by
a co-rotating optical lattice superimposed on the rotating BEC. We study the
effects of two different types of optical lattice, triangular and square. With
both geometries we see an orientation locking between the vortex and the
optical lattices. At sufficient intensity the square optical lattice induces a
structural cross-over in the vortex lattice.Comment: 4 pages, 6 figures. Replaced by final version to appear in Phys. Rev.
Let
Vortex Proliferation in the Berezinskii-Kosterlitz-Thouless Regime on a Two-Dimensional Lattice of Bose-Einstein Condensates
We observe the proliferation of vortices in the Berezinskii-Kosterlitz-Thouless regime on a two-dimensional array of Josephson-coupled Bose-Einstein condensates. As long as the Josephson (tunneling) energy J exceeds the thermal energy T, the array is vortex free. With decreasing J/T, vortices appear in the system in ever greater numbers. We confirm thermal activation as the vortex-formation mechanism and obtain information on the size of bound vortex pairs as J/T is varied
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Shape oscillation of a rotating Bose-Einstein condensate
We present a theoretical and experimental analysis of the transverse monopole
mode of a fast rotating Bose-Einstein condensate. The condensate's rotation
frequency is similar to the trapping frequency and the effective confinement is
only ensured by a weak quartic potential. We show that the non-harmonic
character of the potential has a clear influence on the mode frequency, thus
making the monopole mode a precise tool for the investigation of the fast
rotation regime
Evidence for a breakdown of the Isobaric Multiplet Mass Equation: A study of the A=35, T=3/2 isospin quartet
Mass measurements on radionuclides along the potassium isotope chain have
been performed with the ISOLTRAP Penning trap mass spectrometer. For 35K
T1/2=178ms) to 46K (T1/2=105s) relative mass uncertainties of 2x10-8 and better
have been achieved. The accurate mass determination of 35K (dm=0.54keV) has
been exploited to test the Isobaric Multiplet Mass Equation (IMME) for the
A=35, T=3/2 isospinquartet. The experimental results indicate a deviation from
the generally adopted quadratic form.Comment: 8 pages, 4 figure
Boojums in Rotating Two-Component Bose-Einstein Condensates
A boojum is a topological defect that can form only on the surface of an
ordered medium such as superfluid He and liquid crystals. We study
theoretically boojums appearing between two phases with different vortex
structures in two-component BECs where the intracomponent interaction is
repulsive in one phase and attractive in the other. The detailed structure of
the boojums is revealed by investigating its density distribution, effective
superflow vorticity and pseudospin texture.Comment: 4 pages, 4 figure
Ordered structures in rotating ultracold Bose gases
The characterization of small samples of cold bosonic atoms in rotating
microtraps has recently attracted increasing interest due to the possibility to
deal with a few number of particles per site in optical lattices. We analyze
the evolution of ground state structures as the rotational frequency
increases. Various kinds of ordered structures are observed. For atoms,
the standard scenario, valid for large sytems, is absent, and only gradually
recovered as increases. The vortex contribution to the total angular
momentum as a function of ceases to be an increasing function of
, as observed in experiments of Chevy {\it et al.} (Phys. Rev. Lett.
85, 2223 (2000)). Instead, for small , it exhibits a sequence of peaks
showing wide minima at the values of , where no vortices appear.Comment: 35 pages, 17 figure
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