Fig. 4: Measured and calculated M2 damping.
From: Long-lived zone-boundary magnons in an antiferromagnet
a M2 Raman resonance measured at zero field (green) and 5 T (blue). Solid lines are Lorentzian fits and the linewidth for the μ0H = 0 spectrum is limited by the instrument resolution, indicated by gray vertical strip. b Measured magnetic field dependence of M2 linewidth extracted from Lorentzian fits. Error bars are obtained from Lorentzian model fits to Raman peaks. c M2 magnon decays to lower energy magnons (gray arrows) via a four-magnon process illustrated by the Feynman diagram. The lowest magnon energy is gapped (Δ0) at the Γ point. As a result, four-magnon decay process is restricted (the red region) considering both the energy and momentum conservation. d Calculated magnon decay rate (normalized by Γ point magnon) along a high-symmetry path at zero field and 0 K, showing ~140 fold reduction for the zone-boundary magnons.
