Evaluating the Structural Basis for Polar Altermagnet Candidate Ca3(Ru,Ti)2O7
Abstract
The interplay between polar and altermagnetic orders remains largely unexplored in the broader landscape of correlated electron systems. Density functional theory (DFT) within the PBEsol + U treatment propose Ca3Ru2O7 as a polar altermagnet, reliant on the transformation of the experimentally reported Bb21m phase to a lower symmetry Pn21a structure. Here, we perform a targeted search for the Pn21a phase using synchrotron X-ray diffraction on single crystals of Ca3Ru2O7 and Ca3(Ru0.99Ti0.01)2O7. No diffraction signature of the Pn21a structure is detected down to 20 K within experimental limits. Through diffraction simulations, we translate this result into a quantitative upper bound on the symmetry breaking distortion amplitude, which we find to be significantly smaller than the DFT predicted distortion. Our DFT calculations further motivate dilute Ti substitution (≲ 2%) as an alternative route to stabilize the low symmetry phase, for which we again find no clear evidence for this putative Pn21a structure that hosts altermagnetism. Our findings indicate that PBEsol + U over-stabilizes a Pn21a distortion, and the measured bounds provide benchmark for future calculations. Ti substitution exceeding ∼3% reveals a chemically tunable polar altermagnetic phase within the Bb21m structure and we theoretically demonstrate that the spin-splitting can be tuned by Ti substitution. By combining DFT, diffraction simulations and synchrotron X-ray measurements, our study demonstrates a general methodology to quantify subtle structural distortions that underlie emergent electronic and magnetic phases.
Versions
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BibTeX
@misc{saha2026evaluating,
title = {{Evaluating the Structural Basis for Polar Altermagnet Candidate Ca$_3$(Ru,Ti)$_2$O$_7$}},
author = {Akash Saha and Yihuang Xiong and Vladimir A. Stoica and Subin Mali and Aaron Pearre and Saugata Sarker and Huaiyu Wang and Yufei Zhao and Evguenia Karapetrova and Yu Wang and Jadupati Nag and Zachary W. Hazenstab and Seng Huat Lee and Long-Qing Chen and Geoffroy Hautier and Binghai Yan and Zhiqiang Mao and Venkatraman Gopalan},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.16181},
eprint = {2606.16181},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.16181},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Evaluating the Structural Basis for Polar Altermagnet Candidate Ca_3(Ru,Ti)_2O_7
AU - Akash Saha
AU - Yihuang Xiong
AU - Vladimir A. Stoica
AU - Subin Mali
AU - Aaron Pearre
AU - Saugata Sarker
AU - Huaiyu Wang
AU - Yufei Zhao
AU - Evguenia Karapetrova
AU - Yu Wang
AU - Jadupati Nag
AU - Zachary W. Hazenstab
AU - Seng Huat Lee
AU - Long-Qing Chen
AU - Geoffroy Hautier
AU - Binghai Yan
AU - Zhiqiang Mao
AU - Venkatraman Gopalan
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2606.16181
UR - https://arxiv.org/abs/2606.16181
AB - The interplay between polar and altermagnetic orders remains largely unexplored in the broader landscape of correlated electron systems. Density functional theory (DFT) within the PBEsol + U treatment propose Ca_3Ru_2O_7 as a polar altermagnet, reliant on the transformation of the experimentally reported Bb2_1m phase to a lower symmetry Pn2_1a structure. Here, we perform a targeted search for the Pn2_1a phase using synchrotron X-ray diffraction on single crystals of Ca_3Ru_2O_7 and Ca_3(Ru_0.99Ti_0.01)_2O_7. No diffraction signature of the Pn2_1a structure is detected down to 20 K within experimental limits. Through diffraction simulations, we translate this result into a quantitative upper bound on the symmetry breaking distortion amplitude, which we find to be significantly smaller than the DFT predicted distortion. Our DFT calculations further motivate dilute Ti substitution (≲ 2%) as an alternative route to stabilize the low symmetry phase, for which we again find no clear evidence for this putative Pn2_1a structure that hosts altermagnetism. Our findings indicate that PBEsol + U over-stabilizes a Pn2_1a distortion, and the measured bounds provide benchmark for future calculations. Ti substitution exceeding ∼3% reveals a chemically tunable polar altermagnetic phase within the Bb2_1m structure and we theoretically demonstrate that the spin-splitting can be tuned by Ti substitution. By combining DFT, diffraction simulations and synchrotron X-ray measurements, our study demonstrates a general methodology to quantify subtle structural distortions that underlie emergent electronic and magnetic phases.
ER -