Description
Altermagnetism, a recently established class of magnetic order, combines key features of ferromagnetism and Néel antiferromagnetism, leading to unconventional spin splitting without net magnetization. Building on our previous works [PRB 112, 184501 (2025); PRB 113, 024518 (2026); arXiv:2603.12897] on unconventional superconductivity in single-band treatment, we here investigate the crucial role of sublattice degrees of freedom in generating exotic pairing states in two-dimensional altermagnetic systems.
We consider zero-momentum, static superconducting order parameters $Δ_{a\alpha, b\beta}(\mathbf{k})$ where the sublattice (a,b) and spin ($\alpha$, $\beta$) indices are treated on equal footing. The presence of two sublattices qualitatively enriches the pairing structure: by viewing the sublattice index as a pseudospin degree of freedom, its interplay with the physical spin expands the pairing space to 16 distinct channels, in contrast to the four channels available in single-band systems.
This enlarged pairing manifold naturally supports a wide range of unconventional superconducting phenomena. In particular, it provides a unified framework for understanding field-induced superconductivity and pairing transitions, reminiscent of those observed in uranium-based ferromagnetic superconductors [Science 309, 1343 (2005); Nat. Phys. 15, 1250 (2019)] and CeRh$_2$As$_2$ [Science 373, 1012 (2021)], as well as η-pairing recently reported in monolayer FeSe [PRL 136, 066502 (2026)].
| I am the presenting author | Yes |
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