Constraints on superconducting pairing in altermagnets

Abstract

Superconductivity in the recently discovered altermagnetic materials hosts large prospects for both fundamental physics and technological applications. In this work, we show that a characteristic spin-sublattice locking in altermagnets puts severe constraints on possible superconducting pairing. In particular, by considering the archetypical two-band model for a dx2−y2-wave altermagnet on a square lattice, we uncover that the most common form of superconductivity, uniform s-wave spin-singlet pairing is not possible to achieve in altermagnets. Instead, we find that the most likely forms of spin-singlet pairing have dx2−y2- or extended s-wave symmetry. We also find that the simplest form of equal-spin-triplet p-wave pairing is not allowed, but only a mixed-spin-triplet p-wave state can exist. We verify these constraints on the superconducting pairing also within an interaction-induced model of altermagnetism, where we further establish their validity for finite-momentum pairing. Additionally we discuss the possible pairing symmetries for odd-frequency superconducting pairing. Due to the generality of our results, they are applicable to both intrinsic superconductivity and proximity-induced superconductivity in altermagnet-superconductor hybrid junctions.

Source-reported materials — not catalogue approval

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