Precision measurement of spin-dependent interaction strengths for spin-1 and spin-2 87Rb atoms

TL;DR

This paper presents precise measurements of spin-dependent interaction strengths in ultracold 87Rb atoms in different hyperfine states, using collisionally driven spin dynamics in optical lattices to test theoretical models and determine magnetic ground states.

Contribution

It introduces a novel method based on coherence in spin dynamics to directly measure interaction parameters in ultracold atoms, providing experimental validation of theoretical predictions.

Findings

Measured scattering length differences agree within 20% of theory.

Confirmed ferromagnetic ground state in 87Rb f=1 manifold.

Data suggests antiferromagnetic or cyclic phase in 87Rb f=2 manifold.

Abstract

We report on precision measurements of spin-dependent interaction-strengths in the 87Rb spin-1 and spin-2 hyperfine ground states. Our method is based on the recent observation of coherence in the collisionally driven spin-dynamics of ultracold atom pairs trapped in optical lattices. Analysis of the Rabi-type oscillations between two spin states of an atom pair allows a direct determination of the coupling parameters in the interaction hamiltonian. We deduce differences in scattering lengths from our data that can directly be compared to theoretical predictions in order to test interatomic potentials. Our measurements agree with the predictions within 20%. The knowledge of these coupling parameters allows one to determine the nature of the magnetic ground state. Our data imply a ferromagnetic ground state for 87Rb in the f=1 manifold, in agreement with earlier experiments performed without the optical lattice. For 87Rb in the f=2 manifold the data points towards an antiferromagnetic ground state, however our error bars do not exclude a possible cyclic phase.