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arXiv · 2602.05894

Topological piezomagnetic effect in two-dimensional Dirac quadrupole altermagnets

H. Radhakrishnan·B. Bell·C. Ortix·J. W. F. Venderbos
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Abstract

Altermagnets provide a natural platform for studying and exploiting piezomagnetism. In this paper, we introduce a class of insulating altermagnets in two dimensions (2D) referred to as Dirac quadrupole altermagnets, and show based on microscopic minimal models that the orbital piezomagnetic polarizability of such altermagnets has a topological contribution described by topological response theory. The essential low-energy electronic structure of Dirac quadrupole altermagnets can be understood from a gapless parent phase (i.e., the Dirac quadrupole semimetal), which has important implications for their response to external fields. Focusing on the strain-induced response, here we demonstrate that the topological piezomagnetic effect is a consequence of the way in which strain affects the Dirac points forming a quadrupole. We consider two microscopic models: a spinless two-band model describing a band inversion of $s$ and $d$ states, and a Lieb lattice model with collinear N\'eel order. The latter is a prototypical minimal model for altermagnetism in 2D and is realized in a number of recently proposed material compounds, which are discussed.

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H. Radhakrishnan, B. Bell, C. Ortix, J. W. F. Venderbos. 2026-02-05. Topological piezomagnetic effect in two-dimensional Dirac quadrupole altermagnets. https://arxiv.org/abs/2602.05894

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