Geometric Phases generated by the non-trivial spatial topology of static vector fields coupled to a neutral spin-endowed particle. Application to 171Yb atoms trapped in a 2D optical lattice

TL;DR

This paper explores the geometric phases arising from the topology of spatially varying magnetic fields interacting with neutral spin-1/2 particles, specifically applied to cold 171Yb atoms in 2D optical lattices, with a focus on perturbative analysis and experimental control.

Contribution

It introduces a perturbation scheme for geometric phases in non-Abelian gauge fields generated by spatially varying magnetic fields, applied to cold atom systems in optical lattices.

Findings

Explicit calculation of geometric magnetic fields for 171Yb atoms in optical lattices.

Second-order corrections can be minimized with appropriate light intensity.

Confined atoms experience upward-pointing geometric fields within optical lattices.

Abstract

We have constructed the geometric phases emerging from the non-trivial topology of a space-dependent magnetic field, interacting with the spin magnetic moment of a neutral particle. Our basic tool is the local unitary transformation which recasts the magnetic spin interaction under a diagonal form. Rewriting the kinetic term in the "rotated" frame requires the introduction of non-Abelian covariant derivatives, involving the gradients of the Euler angles which define the orientation of the local field. Within the rotated frame, we have built a perturbation scheme,assuming that the longitudinal non-Abelian field component dominates the transverse ones, to be evaluated to second-order. The geometry embedded in the longitudinal gauge vector field and its curl, the geometric magnetic field, is described by the associated Aharonov-Bohm phase. As an illustration, we study the physics of cold 171Yb atoms dressed by two sets of circularly polarized beams, forming square or triangular 2D optical lattices. The geometric field is computed explicitly from the Euler angles. The magnitude of 2nd-order corrections due to transverse fields can be reduced to the percent level by a choice of light intensity which keeps the dressed atom loss rate below 5 s^{-1}. An auxiliary optical lattice confines the atoms within 2D domains where the geometric field is pointing upward.