title: Theory of electromagnons in the multiferroic Mn perovskites: the vital role of higher harmonic components of the spiral spin order.
abstract: We study theoretically the electromagnon and its optical spectrum (OS) of the terahertz-frequency regime in the magnetic-spiral-induced multiferroic phases of the rare-earth-metal (R) Mn perovskites, RMnO3, taking into account the spin-angle modulation or the higher harmonics of the spiral spin configuration, which has been missed so far. A realistic spin Hamiltonian, which gives phase diagrams in agreement with experiments, resolves a puzzle, i.e., the double-peak structure of the OS with a larger low-energy peak originating from magnon modes hybridized with the zone-edge state. We also predict the magnon branches associated with the electromagnon, which can be tested by neutron-scattering experiment.
authors.affiliation: Department of Applied Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. mochizuki@erato-mf.t.u-tokyo.ac.jp
authors.forename: Masahito
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Nobuo
authors.initials: N
authors.lastname: Furukawa
authors.forename: Naoto
authors.initials: N
authors.lastname: Nagaosa