Anomalous phonon selection rules and Raman optical activity in RuO ₂
- 1Department of Physics, National University of Singapore, Singapore 117551, Singapore.
- 2Department of Physics, State Key Laboratory of Quantum Functional Materials, and Guangdong Basic Research Center of Excellence for Quantum Science, Southern University of Science and Technology (SUSTech), Shenzhen, Guangdong 518055, China.
Abstract
Breakdown of selection rules and emergence of optical activity in Raman spectroscopy typically signal symmetry-breaking events essential for understanding novel phases of solids. Here, we apply our recently developed rotational anisotropy Raman spectroscopy technique to single-crystal ruthenium dioxide-a compound of recent interest as a candidate workhorse material for altermagnetism yet whose magnetic ground state remains under intense debate. Our data reveal a salient breakdown of selection rules for zone-center phonons, accompanied by clear splitting in the angle-dependent polarimetry plots for the two opposite helicity-nonconserving circularly polarized scattering channels. These observations provide definitive evidence of a previously overlooked symmetry-breaking event, involving either spatial or time-reversal symmetry. In either scenario, the underlying mechanism is likely a bulk hidden order parameter, potentially involving multipole moments of Ruthenium(IV) set by the local crystal field environment. Our work demonstrates how subtle symmetry-breaking events can manifest through lattice dynamics and calls for renewed experimental and theoretical efforts to map the phase diagram of ruthenium dioxide as a system poised near quantum phase transition boundaries.
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BibTeX
@article{cheng2026anomalous,
title = {{Anomalous phonon selection rules and Raman optical activity in RuO ₂}},
author = {Di Cheng and Ao Wu and Hui Pan and Yu-Peng Zhu and Shizhuo Luo and King Yau Yip and Wei Zhang and Ariando Ariando and Chang Liu and Jian-Sheng Wang and Xinwei Li},
journal = {Science Advances},
year = {2026},
month = oct,
doi = {10.1126/sciadv.aeh0887},
url = {https://www.science.org/doi/10.1126/sciadv.aeh0887},
note = {CC BY},
}
RIS
TY - JOUR
TI - Anomalous phonon selection rules and Raman optical activity in RuO ₂
AU - Di Cheng
AU - Ao Wu
AU - Hui Pan
AU - Yu-Peng Zhu
AU - Shizhuo Luo
AU - King Yau Yip
AU - Wei Zhang
AU - Ariando Ariando
AU - Chang Liu
AU - Jian-Sheng Wang
AU - Xinwei Li
PY - 2026
DA - 2026/10/21
JO - Science Advances
DO - 10.1126/sciadv.aeh0887
UR - https://www.science.org/doi/10.1126/sciadv.aeh0887
AB - Breakdown of selection rules and emergence of optical activity in Raman spectroscopy typically signal symmetry-breaking events essential for understanding novel phases of solids. Here, we apply our recently developed rotational anisotropy Raman spectroscopy technique to single-crystal ruthenium dioxide-a compound of recent interest as a candidate workhorse material for altermagnetism yet whose magnetic ground state remains under intense debate. Our data reveal a salient breakdown of selection rules for zone-center phonons, accompanied by clear splitting in the angle-dependent polarimetry plots for the two opposite helicity-nonconserving circularly polarized scattering channels. These observations provide definitive evidence of a previously overlooked symmetry-breaking event, involving either spatial or time-reversal symmetry. In either scenario, the underlying mechanism is likely a bulk hidden order parameter, potentially involving multipole moments of Ruthenium(IV) set by the local crystal field environment. Our work demonstrates how subtle symmetry-breaking events can manifest through lattice dynamics and calls for renewed experimental and theoretical efforts to map the phase diagram of ruthenium dioxide as a system poised near quantum phase transition boundaries.
SN - 2375-2548
ER -