Direct observation of phonon mode with an antisymmetric Raman tensor
Abstract
Phonon angular momentum, characterized by circular or elliptical motion of atoms, plays a decisive role in diverse phenomena, ranging from the phonon Hall effect, phonon magnetic moment, Einstein-de Haas effect, Weyl phonons, and driven chiral phonons. The phonon modes with an antisymmetric Raman tensor, which carry an intrinsic phonon angular momentum in a pseudovector symmetry channel, have been overlooked in the past in the chiral phonon community. Here, we report the detection of this type of phonon mode using polarization-resolved Raman spectroscopy. We observe a phonon at 266cm−1 in the antiferromagnetic chiral phase of Cr2O3 in the A2-pseudovector symmetry channel. This A2 mode's frequency and the elliptical motion are captured by first-principles phonon calculations, which treat both lattice and spins on an equal footing as 'slow' degrees of freedom. This mode gets Raman activity due to the presence of Cr vacancies in Cr2O3 that locally break the twofold rotational symmetry perpendicular to the threefold axis. Our results provide a new way to detect the novel symmetry-forbidden A2 phonon modes with an antisymmetric Raman tensor in a pseudovector symmetry channel.
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BibTeX
@misc{wu2026direct,
title = {{Direct observation of phonon mode with an antisymmetric Raman tensor}},
author = {Shangfei Wu and Shang Ren and Kai Du and Xianghan Xu and Sang-Wook Cheong and David Vanderbilt and Girsh Blumberg},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18332},
eprint = {2609.18332},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18332},
}
RIS
TY - UNPB
TI - Direct observation of phonon mode with an antisymmetric Raman tensor
AU - Shangfei Wu
AU - Shang Ren
AU - Kai Du
AU - Xianghan Xu
AU - Sang-Wook Cheong
AU - David Vanderbilt
AU - Girsh Blumberg
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18332
UR - https://arxiv.org/abs/2609.18332
AB - Phonon angular momentum, characterized by circular or elliptical motion of atoms, plays a decisive role in diverse phenomena, ranging from the phonon Hall effect, phonon magnetic moment, Einstein-de Haas effect, Weyl phonons, and driven chiral phonons. The phonon modes with an antisymmetric Raman tensor, which carry an intrinsic phonon angular momentum in a pseudovector symmetry channel, have been overlooked in the past in the chiral phonon community. Here, we report the detection of this type of phonon mode using polarization-resolved Raman spectroscopy. We observe a phonon at 266cm^−1 in the antiferromagnetic chiral phase of Cr_2O_3 in the A_2-pseudovector symmetry channel. This A_2 mode's frequency and the elliptical motion are captured by first-principles phonon calculations, which treat both lattice and spins on an equal footing as 'slow' degrees of freedom. This mode gets Raman activity due to the presence of Cr vacancies in Cr_2O_3 that locally break the twofold rotational symmetry perpendicular to the threefold axis. Our results provide a new way to detect the novel symmetry-forbidden A_2 phonon modes with an antisymmetric Raman tensor in a pseudovector symmetry channel.
ER -