Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

The Dzyaloshinskii-Moriya interaction is vital in stabilizing the magnetic phases of chiral magnets, but how does this interaction manifest itself in the magnetic excitation spectrum? The authors perform high resolution time-domain terahertz spectroscopy experiments and time-of-flight neutron scattering experiments to investigate the low-energy magnetic response of the newly discovered insulating and magnetoelectric chiral magnet Cu${}₂$OSeO${}₃$. Transmission and polarimetry experiments performed as a function of magnetic field uncover new magnetic excitations, detect the topologically nontrivial skyrmion phase, and reveal unexpected magnon dynamics. These observations are consistent with the presence of an exceptionally strong Dzyaloshinskii-Moriya interaction in this material and highlight the need for its inclusion if the magnetic response of such chiral magnets is to be completely understood..