Nonlinear Elimination of Spin-Exchange Relaxation of High Magnetic Moments

TL;DR

This paper demonstrates both experimentally and theoretically that nonlinear spin-exchange interactions can eliminate relaxation of high magnetic moments in alkali vapor, revealing new ways to control magnetic coherence.

Contribution

It introduces the concept that nonlinear spin-exchange interactions can eliminate relaxation of high magnetic moments, a phenomenon not previously understood.

Findings

Relaxation diminishes for high alkali densities due to nonlinear effects.

Experimental and theoretical evidence of relaxation elimination at high magnetic moments.

Threshold magnetic field remains the same as in the linear Larmor case.

Abstract

Relaxation of the Larmor magnetic moment by spin-exchange collisions has been shown to diminish for high alkali densities, resulting from the linear part of the collisional interaction. In contrast, we demonstrate both experimentally and theoretically the elimination of spin-exchange relaxation of high magnetic moments (birefringence) in alkali vapor. This elimination originates from the nonlinear part of the spin-exchange interaction, as a scattering process of the Larmor magnetic moment. We find counter-intuitively that the threshold magnetic field is the same as in the Larmor case, despite the fact that the precession frequency is twice as large.