Resonant spin amplification meets electron spin resonance in $n$-GaAs

TL;DR

This paper investigates how an external oscillating magnetic field affects resonant spin amplification in n-GaAs, revealing a double-peaked electron spin resonance and demonstrating control over spin polarization via radio-frequency fields.

Contribution

The study introduces a comprehensive quaternion-based theory that explains the modified RSA phenomena under oscillating fields, enabling precise control of electron spin states.

Findings

Double-peaked electron spin resonance observed

Frequency splitting scales linearly with field amplitude

Oscillating field can suppress or induce RSA conditions

Abstract

Periodic excitation of electron spin polarization by consecutive laser pulses in phase with Larmor spin precession about a magnetic field results in resonant spin amplification (RSA). We observe a drastic modification of RSA in $n$-doped bulk GaAs under the influence of external oscillating magnetic field. We find a double-peaked electron spin resonance instead of a single-peaked resonance expected without optical pumping. The frequency splitting increases linearly with amplitude of field oscillations, while the spin deviation increases quadratically. Moreover, we show that the oscillating field can both significantly suppress RSA and induce new conditions for resonance. Using quaternions to describe spin rotations, we develop a theory that simultaneously considers spin precession, decay, and amplification and reproduces the entire set of the experimental data. Using the radio-frequency field allows one to control the conditions of RSA and achieve fine tuning of average spin polarization without modifying the parameters of optical pumping.