Origin of anomalous polarization leakage near 350 cm−1

Determine the origin of the anomalous polarization-leakage intensity of the approximately 350 cm−1 E-mode phonon in the RR scattering geometry of antiferromagnetic Cr2O3, including whether it is related to polarization rotations within the antiferromagnetic phase.

Background

The paper analyzes polarization-resolved Raman spectra of Cr2O3 using RR and RL circular-polarization scattering geometries. Polarization leakage from optical elements is estimated from the known A1 and E bulk phonons and is generally removable using an average leakage ratio of approximately 2%.

The E-mode phonon near 350 cm−1 is anomalous: it exhibits a leakage ratio of about 6% into the RR geometry, and the leakage cannot be fully removed using the standard procedure. The anomalous leakage appears only below the antiferromagnetic transition temperature, suggesting a possible connection to polarization rotations in the antiferromagnetic phase, but the paper does not resolve its origin.

References

The origin of the anomalous leakage intensity for the 350\,\cm-1 mode is unknown. It might be related to the polarization rotations within the AFM phase, as the leakage intensity in the $RR$ scattering geometry only appears below $T_\text{N}$~[Fig.~\ref{Fig1_RR_RL} of main text].

— Direct observation of phonon mode with an antisymmetric Raman tensor  (2609.18332 - Wu et al., 16 Sep 2026) in Supplementary Materials, Section “Removal of polarization leakage”