Low energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu${}_2$OSeO${}_3$

Abstract

In this work, we present a comprehensive study of the low energy optical magnetic response of the skyrmionic Mott insulator Cu${}_2$OSeO${}_3$ via high resolution time-domain THz spectroscopy. In zero field, a new magnetic excitation not predicted by spin-wave theory with frequency $f$ = 2.03 THz is observed and shown, with accompanying time-of-flight neutron scattering experiments, to be a zone folded magnon from the $\mathrm{R}$ to $\mathrm{\Gamma }$ points of the Brillouin zone. Highly sensitive polarimetry experiments performed in weak magnetic fields, ${\mu }_0$H $<$ 200 mT, observe Faraday and Kerr rotations which are proportional to the sample magnetization, allowing for optical detection of the skyrmion phase and construction of a magnetic phase diagram. From these measurements, we extract a critical exponent of $\beta$ = 0.35 $\pm$ 0.04, in good agreement with the expected value for the 3D Heisenberg universality class of $\beta$ = 0.367. In large magnetic fields, ${\mu }_0$H $>$ 5 T, we observe the magnetically active uniform mode of the ferrimagnetic field polarized phase whose dynamics as a function of field and temperature are studied. In addition to extracting a $g_{\text{eff}}$ = 2.08 $\pm$ 0.03, we observe the uniform mode to decay through a non-Gilbert damping mechanism and to possesses a finite spontaneous decay rate, ${\Gamma }_0$ $\approx$ 25 GHz, in the zero temperature limit. Our observations are attributed to Dzyaloshinkii-Moriya interactions, which have been proposed to be exceptionally strong in Cu${}_2$OSeO${}_3$ and are expected to impact the low energy magnetic response of such chiral magnets.

13 pages, 8 figures

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Cited by in corpus (9)

• Spinon magnetic resonance of quantum spin liquids
• New Microscopic Magnetic Hamiltonian for Exotic Spin Textures in Metals
• Strong magneto-optical effects in ACr2O4 A=Fe, Co spinel oxides generated by tetrahedrally coordinated transition metal ions
• Low energy magnons in the chiral ferrimagnet ${\text{Cu}}_2{\text{OSeO}}_3$: a coarse-grained approach
• Inelastic light scattering in the spin cluster Mott insulator Cu${}_2$OSeO${}_3$
• Coupled dynamics of long-range and internal spin cluster order in Cu${}_2$OSeO${}_3$
• Quintuplet condensation in the skyrmionic insulator Cu2OSeO3 at ultrahigh magnetic fields
• The influence of antiferromagnetic spin cantings on the magnetic helix pitch in cubic helimagnets
• Seeded Chemical Vapor Transport Growth of Cu${}_2$OSeO${}_3$