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Updated: Jul 11, 2025

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals
Published on: August 15, 2018
Large effective magnetic fields from chiral phonons in rare-earth halides
Jiaming Luo1,2, Tong Lin1, Junjie Zhang1
1Department of Materials Science and Nano Engineering, Rice University, Houston, TX 77005, USA.
Abstract:
Time-reversal symmetry (TRS) is pivotal for materials' optical, magnetic, topological, and transport properties. Chiral phonons, characterized by atoms rotating unidirectionally around their equilibrium positions, generate dynamic lattice structures that break TRS. Here, we report that coherent chiral phonons, driven by circularly polarized terahertz light pulses, polarize the paramagnetic spins in cerium fluoride in a manner similar to that of a quasi-static magnetic field on the order of 1 tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found that the transient magnetization is only excited by pulses resonant with phonons, proportional to the angular momentum of the phonons, and growing with magnetic susceptibility at cryogenic temperatures. The observation quantitatively agrees with our spin-phonon coupling model and may enable new routes to investigating ultrafast magnetism, energy-efficient spintronics, and nonequilibrium phases of matter with broken TRS.
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