Symmetry plays a key role in determining the physical properties of materials. By Neumann's principle, the properties of a material are invariant under the symmetry operations of the space group to which the material belongs. Continuous phase transitions are associated with a spontaneous reduction in symmetry. (For example, the onset of ferromagnetism spontaneously breaks time reversal symmetry.) Much less common are examples where proximity to a continuous phase transition leads to an increase in symmetry. Here, we find an emergent tetragonal symmetry close to an apparent charge density wave (CDW) bicritical point in a fundamentally orthorhombic material, ErTe3, for which the CDW phase transitions are tuned via anisotropic strain. The underlying structure of the material remains orthorhombic for all applied strains, including at the bicritical point, due to a glide plane symmetry in the crystal structure. Nevertheless, the observation of a divergence in the anisotropy of the in-plane elastoresistivity reveals an emergent electronic tetragonality near the bicritical point.
@article{arxiv.2306.14755,
title = {Emergent Tetragonality in a Fundamentally Orthorhombic Material},
author = {Anisha G. Singh and Maja D. Bachmann and Joshua J. Sanchez and Akshat Pandey and Aharon Kapitulnik and Jong Woo Kim and Philip J. Ryan and Steven A. Kivelson and Ian R. Fisher},
journal= {arXiv preprint arXiv:2306.14755},
year = {2024}
}