Abstract
We report the observation of strongly ferromagnetic F=1 spinor Bose-Einstein condensates of Li7 atoms. The condensates are generated in an optical dipole trap without using magnetic Feshbach resonances, so that the condensates have internal spin degrees of freedom. Studying the nonequilibrium spin dynamics, we have measured the ferromagnetic spin interaction energy and determined the s-wave scattering length difference among total spin f channels to be af=2−af=0=−18(3) Bohr radius. This strong collision-channel dependence leads to a large variation in the condensate size with different spin composition. We were able to excite a radial monopole mode after a spin-flip transition between the |mF=0〉 and |mF=1〉 spin states. From the experiments, we estimated the scattering length ratio af=2/af=0=0.27(6), and determined af=2=7(2) and af=0=25(5) Bohr radii, respectively. The results indicate the spin-dependent interaction energy of our system is as large as 46% of the condensate chemical potential.1 MoreReceived 11 June 2020Accepted 28 August 2020DOI:https://doi.org/10.1103/PhysRevResearch.2.033471Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBose-Einstein condensatesUltracold collisionsAtomic, Molecular & Optical
Highlights
The spinor Bose gas of ultracold atoms has been a pristine platform for studying multi-component superfluid systems like He-3 [1] and exotic superconductors [2]
The BECs of 7Li were prepared in the |mz = 0 (|0 ) state under 1 G of magnetic field along the z direction
We reduced the magnetic field to B f in 1.4 ms, and a density profile of each spin state (n1, n0, n−1) was recorded using spin-separated absorption imaging after a variable hold time th
Summary
The spinor Bose gas of ultracold atoms has been a pristine platform for studying multi-component superfluid systems like He-3 [1] and exotic superconductors [2]. In such systems the condensate wavefunction has additional spin degrees of freedom and is described by a vector or tensor order parameter [3,4]. The strong ferromagnetic spin interactions provide new opportunities to experimentally investigate the complex interplays between magnetic order and superfluidity [13,14,15,16,17,18], universal coarsening dynamics after a quantum phase transition [19,20,21,22], and to explore rich phases in optical lattices [23,24].
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