title: Electromagnons in the spin collinear state of a triangular lattice antiferromagnet.
abstract: Terahertz time-domain spectroscopy was performed to directly probe the low-energy (1-5 meV) electrodynamics of triangular lattice antiferromagnets CuFe(1-x)Ga(x)O2 (x=0.00, 0.01, and 0.035). We discovered an electromagnon (electric-field-active magnon) excitation at 2.3 meV in the paraelectric ↑↑↓↓ collinear magnetic phase, while this electromagnon vanishes in the ferroelectric helimagnetic phase. Anticorrelation with noncollinear magnetism excludes the exchange-striction mechanism as the origin of dynamical magnetoelectric coupling, and hence evidences the observation of a spin-orbit coupling mediated electromagnon in the present compound.
authors.affiliation: Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Seki
authors.forename: N
authors.initials: N
authors.lastname: Kida
authors.forename: S
authors.initials: S
authors.lastname: Kumakura
authors.forename: R
authors.initials: R
authors.lastname: Shimano
authors.forename: Y
authors.initials: Y
authors.lastname: Tokura