Theory of the Ferroaxial Charge Density Wave in 1T-TiSe2
Abstract
Recent experiments using strain to probe the charge-density wave (CDW) of 1T-TiSe2 have uncovered additional transitions and broken symmetries inside the CDW state. The elastocaloric effect reveals a second transition below TCDW, which elastoresistivity shows to be associated with ferroaxial order, breaking all vertical mirror symmetries while preserving inversion. In addition, at even lower temperatures, a diverging nematic susceptibility has been reported through elastoresistivity. In this work, we argue that this rich phenomenology cannot be explained by the standard L1- CDW order parameter, and instead requires the existence of a secondary CDW order parameter. Based on symmetry, microscopic, and diffraction considerations, we propose this subleading CDW to have L2- symmetry. By analyzing the Landau theory of coupled L1- and L2- orders in the presence of strain, we reproduce the phase boundaries observed in the elastocaloric measurements and the emergence of ferroaxial order below the CDW transition. Moreover, the model supports a third threefold-rotational symmetry breaking transition at lower temperatures, consistent with the reported divergence of the nematic susceptibility.
Related
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BibTeX
@misc{maccari2026theory,
title = {{Theory of the Ferroaxial Charge Density Wave in 1T-TiSe$_2$}},
author = {Ilaria Maccari and Rafael M. Fernandes and Fernando de Juan and Maria N. Gastiasoro},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03478},
eprint = {2611.03478},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03478},
}
RIS
TY - UNPB
TI - Theory of the Ferroaxial Charge Density Wave in 1T-TiSe_2
AU - Ilaria Maccari
AU - Rafael M. Fernandes
AU - Fernando de Juan
AU - Maria N. Gastiasoro
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03478
UR - https://arxiv.org/abs/2611.03478
AB - Recent experiments using strain to probe the charge-density wave (CDW) of 1T-TiSe_2 have uncovered additional transitions and broken symmetries inside the CDW state. The elastocaloric effect reveals a second transition below T_CDW, which elastoresistivity shows to be associated with ferroaxial order, breaking all vertical mirror symmetries while preserving inversion. In addition, at even lower temperatures, a diverging nematic susceptibility has been reported through elastoresistivity. In this work, we argue that this rich phenomenology cannot be explained by the standard L_1^- CDW order parameter, and instead requires the existence of a secondary CDW order parameter. Based on symmetry, microscopic, and diffraction considerations, we propose this subleading CDW to have L_2^- symmetry. By analyzing the Landau theory of coupled L_1^- and L_2^- orders in the presence of strain, we reproduce the phase boundaries observed in the elastocaloric measurements and the emergence of ferroaxial order below the CDW transition. Moreover, the model supports a third threefold-rotational symmetry breaking transition at lower temperatures, consistent with the reported divergence of the nematic susceptibility.
ER -