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arXiv · 2411.09761

An EFT for anisotropic anti-ferromagnets: gapped Goldstones, pseudo-Goldstones, and phase transitions

Pier Giuseppe Catinari·Angelo Esposito·Shashin Pavaskar
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Abstract

We build and discuss a low energy effective field theory for anisotropic anti-ferromagnets in presence of an external magnetic field. Such an effective theory is simple yet rich, and features a number of phenomena such as the appearance of gapped Goldstones, pseudo-Goldstones and a "spin flop" phase transition, all within the regime of validity of the theory. We also discuss in detail, the quantization procedure of the free theory in the presence of a magnetic field, which is made non-trivial by the presence of a single-time derivative term. This class of materials make a precious test field for exotic phenomena in quantum field theory. Moreover, we explicitly perform the matching of the effective theory to the short distance theory of a specific anti-ferromagnet, namely, nickel oxide. The latter is particularly relevant in light of recent proposals of employing this material towards the hunt for light dark matter. As a byproduct of our study, we also re-evaluate the role played by discrete symmetries in magnetic materials, presenting it in a way that is completely consistent with the proper low energy EFT ideology.

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Pier Giuseppe Catinari, Angelo Esposito, Shashin Pavaskar. 2025-08-07. An EFT for anisotropic anti-ferromagnets: gapped Goldstones, pseudo-Goldstones, and phase transitions. https://doi.org/10.1103/msy3-ztxr

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