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Dynamical magneto-electric coupling in helical magnets

Hosho Katsura·Alexander V. Balatsky·Naoto Nagaosa
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Abstract

Collective mode dynamics of the helical magnets coupled to electric polarization via spin-orbit interaction is studied theoretically. The soft modes associated with the ferroelectricity are not the transverse optical phonons, as expected from the Lyddane-Sachs-Teller relation, but are the spin waves hybridized with the electric polarization. This leads to the Drude-like dielectric function $ε(ω)$ in the limit of zero magnetic anisotropy. There are two more low-lying modes; phason of the spiral and rotation of helical plane along the polarization axis. The roles of these soft modes in the neutron scattering and antiferromagnetic resonance are revealed, and a novel experiment to detect the dynamical magneto-electric coupling is proposed.

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Hosho Katsura, Alexander V. Balatsky, Naoto Nagaosa. 2006-02-23. Dynamical magneto-electric coupling in helical magnets. https://doi.org/10.1103/physrevlett.98.027203

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