Creation and detection of skyrmions in a Bose-Einstein condensate

We present the first experimental realization and characterization of two-dimensional skyrmions and half-skyrmions in a spin-2 Bose-Einstein condensate. The continuous rotation of the local spin of the skyrmion through an angle of pi (and half-skyrmion through an angle of pi/2) across the cloud is confirmed by the spatial distribution of the three spin states as parameterized by the bending angle of the ell-vector. The winding number, w = (0, 1, 2), of the skyrmions is confirmed through matter-wave interference.

💡 Research Summary

The authors report the first experimental creation and detailed characterization of two‑dimensional skyrmions and half‑skyrmions (merons) in a spin‑2 Bose‑Einstein condensate of ^87Rb atoms. Starting from a fully polarized condensate in the |F = 2, m_F = 2⟩ state, they apply a pair of Raman laser beams (σ⁻ and σ⁺) in a 5 µs diabatic pulse. The σ⁻ beam carries a Laguerre‑Gaussian (LG⁻¹) mode while the σ⁺ beam is a simple Gaussian; together they drive two‑photon transitions to the |2, 0⟩ and |2, −2⟩ Zeeman sublevels. Because of the orbital angular momentum of the LG beam, the transferred atoms acquire azimuthal phase windings of w = 1 and w = 2, respectively, while the original |2, 2⟩ component remains unwound (w = 0). The resulting order parameter can be written as Ψ(r) = √n(r)