An effective magnetic field from optically driven phonons

TL;DR

This paper demonstrates how optically driven phonons can generate an effective magnetic field in materials, enabling control of spin dynamics and potentially influencing electronic phase topology.

Contribution

It introduces a method to induce an effective magnetic field through nonlinear phonon mode mixing driven by light, a novel approach for manipulating magnetic and electronic properties.

Findings

Excitation of multiple lattice modes can mimic magnetic fields.

Controlled phase relationships enable spin precession.

Potential to influence electronic phase topology.

Abstract

Light fields at THz and mid-infrared frequencies allow for the direct excitation of collective modes in condensed matter, which can be driven to large amplitudes. For example, excitation of the crystal lattice, has been shown to stimulate insulator-metal transitions, melt magnetic order, or enhance superconductivity. Here, we generalize these ideas and explore the simultaneous excitation of more than one lattice mode, which are driven with controlled relative phases. This nonlinear mode mixing drives rotations as well as displacements of the crystal-field atoms, mimicking the application of a magnetic field and resulting in the excitation of spin precession in the rare-earth orthoferrite $ErFeO_3$. Coherent control of lattice rotations may become applicable to other interesting problems in materials research, for example as a way to affect the topology of electronic phases.