Nonlinear subharmonic response and spectral shifts in bichromatically driven atomic magnetic resonance
Phys. Rev. A 114, 042811 – Published 15 October, 2026
DOI: https://doi.org/10.1103/dgmd-fdmh
Abstract
Subharmonic resonances can provide spectral observables beyond the main atomic magnetic-resonance spectrum, but their physical origin and use under bichromatic driving remain unclear. We study cesium-vapor magnetic resonance driven by two rf fields. The first field serves as a calibrated local reference. We infer the second field's frequency offset from the multiplet center and its amplitude from the internal splitting. The amplitude calibration includes detuning and off-resonant corrections. Two optical preparation and readout configurations select distinct spin multipoles while preserving the relative magnetic-field geometry. Orientation and alignment spectra exhibit triplet and quintuplet Floquet multiplets, respectively. A Floquet model explains these rank-dependent structures through multiphoton coupling and off-resonant quasienergy shifts. These results enable frequency-and-amplitude readout of rf fields far from the bare Larmor resonance at a fixed static magnetic field.
