Optical excitation of magnons in an easy-plane antiferromagnet: Application to Sr${}_2$IrO${}_4$

Abstract

We study the interaction of a (classical) light field with the magnetic degrees of freedom in the two-dimensional antiferromagnet Sr${}_2$IrO${}_4$. The reduced space group symmetry of the crystal allows for several channels for spin-operator bilinears to couple to the electric field. Integrating out high-energy degrees of freedom in a Keldysh framework, we derive induced effective fields which enter the equations of motion of the low-energy mode of in-plane rotations which couple to the out-of-plane magnetization. Considering a pump-probe protocol, these induced fields excite magnetization oscillations which can subsequently probed, e.g. using Kerr rotation. We discuss how the induced fields depend on polarization and frequency of the driving light, and our study applies to both resonant and non-resonant regimes. Crucially, the induced fields depend on the two-magnon density of states, thus allowing for further insight into properties of the magnetic excitation spectrum. Furthermore, these effects rely upon (weak) magnon-interactions, and so are beyond a "Floquet magnon" description.

15 pages, 4 figures. (v2) as published, with expanded summary of methods and minor typos corrected

References in corpus (8)

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• Spin current and magneto-electric effect in non-collinear magnets
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Spin Oscillations in Antiferromagnetic NiO Triggered by Circularly Polarized Light
• Electronic Orbital Currents and Polarization in Mott Insulators
• Magnetic couplings, optical spectra, and spin-orbit exciton in 5d electron Mott insulator Sr2IrO4
• Pseudo Jahn-Teller Effect and Magnetoelastic Coupling in Spin-Orbit Mott Insulators
• Pseudospin-lattice coupling in the spin-orbit Mott insulator Sr2IrO4

Cited by in corpus (8)

• Cavity magnon-polaritons in cuprate parent compounds
• Ultrafast optical excitation of magnetic dynamics in van der Waals magnets: Coherent magnons and BKT dynamics in NiPS${}_3$
• Decoupling of static and dynamic criticality in a driven Mott insulator
• Distinct Optical Excitation Mechanisms of a Coherent Magnon in a van der Waals Antiferromagnet
• Modeling multiorbital effects in Sr2IrO4 under strain and a Zeeman field
• Dynamics of photo-induced ferromagnetism in oxides with orbital degeneracy
• Coupling of plasmons to the two-magnon continuum in antiferromagnets
• Optically induced magnetic inertia and magnons from non-Markovian extension of the Landau-Lifshitz-Gilbert equation