• DOI:10.1038/s41567-021-01210-6
• Corpus ID: 221681785

Mirror symmetry breaking in a model insulating cuprate

@article{Torre2020MirrorSB,
  title={Mirror symmetry breaking in a model insulating cuprate},
  author={Alberto de la Torre and Kyle L. Seyler and L. Zhao and Sergio Di Matteo and Mathias S. Scheurer and Y. Li and Bowen Yu and Martin Greven and Subir Sachdev and Michael R. Norman and David Hsieh},
  journal={Nature Physics},
  year={2020},
  volume={17},
  pages={777 - 781}
}

• A. D. L. Torre, K. Seyler, +8 authors D. Hsieh
• Published 14 August 2020
• Physics
• Nature Physics

Among the most actively studied issues in the cuprates are the natures of the pseudogap and strange metal states and their relationship to superconductivity1. There is general agreement that the low-energy physics of the Mott-insulating parent state is well captured by a two-dimensional spin S = 1/2 antiferromagnetic Heisenberg model2. However, recent observations of a large thermal Hall conductivity in several parent cuprates appear to defy this simple model and suggest proximity to a magneto-chiral state that breaks all mirror planes that are perpendicular to the CuO2 layers3–6. Here we use optical second harmonic generation to directly resolve the point group symmetries of the model parent cuprate Sr2CuO2Cl2. We report evidence of an order parameter that breaks all perpendicular mirror planes and is consistent with a magneto-chiral state in zero magnetic field. Although this order is clearly coupled to the antiferromagnetism, we are unable to realize its time-reversed partner by thermal cycling through the antiferromagnetic transition temperature or by sampling different spatial locations. This suggests that the order onsets above the Néel temperature and may be relevant to the mechanism of pseudogap formation. Several cuprate superconductors were recently shown to have chiral phonons. Here second harmonic generation measurements show that antiferromagnetism breaks all mirror symmetries in a related compound, consistent with a chiral state.