Superconductivity from altermagnetic fluctuations: the crucial role of sublattice polarization
Year: 2026
Type: preprint
Abstract: Unconventional superconductivity in correlated systems often appears in the vicinity of a magnetically ordered state. This situation is also relevant for altermagnets, characterized by a nonrelativistic spin-split electronic structure in the presence of Néel order. Many proposed altermagnetic candidates, however, never cross the magnetic instability. We study superconductivity arising from altermagnetic fluctuations in such systems and show that the sublattice polarization (SLP) of the normal-state bands plays a pivotal role in determining the superconducting state. SLP, an inherent property of altermagnetic band structures that persists even without magnetic order, prevents Cooper pairs from forming between different sublattices. This suppresses pairing mediated by the nearest-neighbor antiferromagnetic exchange, which favors spin-singlet superconductivity, and leaves longer-range same-sublattice bonds dominant. When the next-nearest-neighbor exchange is ferromagnetic, as expected for frustration-free Néel order, this results in spin-triplet superconductivity. This mechanism is fundamentally different from that in altermagnets with long-range Néel order, where the spin-split Fermi surfaces favor equal-spin pairing. Finally, when longer-range interactions in the disordered phase instead favor singlet pairing, SLP leads to singlet states with characteristic properties distinct from nearest-neighbor pairing states.
Source: arXiv (Cornell University)
Institutions: University of Copenhagen, Uppsala University
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: Villum Fonden
Award: G2613776651
OpenAlex ID: W7221777761