Larmor frequency dressing by an anharmonic transverse magnetic field

TL;DR

This paper develops a new theoretical model and experimental validation for spin precession under complex magnetic fields, enabling enhanced detection of weak transverse fields using atomic magnetometers.

Contribution

It introduces a novel approach to model spin dynamics with nonresonant, anharmonic magnetic fields, improving the understanding of nonlinear effects in atomic magnetometry.

Findings

Model closely matches experimental data

Nonharmonic fields enable linear response to weak dc fields

Enhanced sensitivity in scalar magnetometers

Abstract

We present a theoretical and experimental study of spin precession in the presence of both a static and an orthogonal oscillating magnetic field, which is nonresonant, not harmonically related to the Larmor precession, and of arbitrary strength. Due to the intrinsic nonlinearity of the system, previous models that account only for the simple sinusoidal case cannot be applied. We suggest an alternative approach and develop a model that closely agrees with experimental data produced by an optical-pumping atomic magnetometer. We demonstrate that an appropriately designed nonharmonic field makes it possible to extract a linear response to a weak dc transverse field, despite the scalar nature of the magnetometer, which normally causes a much weaker, second-order response.