Finite-momentum bound pairs of two electrons in an altermagnetic metal

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Abstract
We solve the two-electron problem on a square lattice with $d$-wave altermagnetism, considering both on-site and nearest-neighbor attractive interactions. The altermagnetic spin-splitting in the single-particle dispersion naturally gives rise to a ground state of two-electron bound pairs with nonzero center-of-mass momentum. The emergence of finite-momentum bound states suggests that altermagnetic spin splitting may favor pairing at nonzero center-of-mass momentum, which could be relevant for proposed Fulde-Ferrell-Larkin-Ovchinnikov superconductivity in altermagnetic systems. Additionally, when the nearest-neighbor attraction is strong, the resulting finite-momentum bound pairs exhibit a mixture of both spin-singlet and spin-triplet characteristics, suggesting the possibility of unconventional superconductors, where spin-singlet and spin-triplet pairings coexist.
Funding Information
  • Australian Research Council (DP240101590)
  • Australian Research Council (FT230100229)
  • Australian Research Council (DP240100248)

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