Altermagnetic-doping interplay as a route to enhanced d-wave pairing in the Hubbard model

TL;DR

This paper explores how altermagnetic materials influence the Hubbard model, revealing enhanced unconventional superconductivity and mixed-symmetry pairing driven by spin anisotropy, with potential implications for higher transition temperatures.

Contribution

It introduces the role of altermagnetic anisotropy in stabilizing and enhancing d-wave and p-wave pairing in the Hubbard model, supported by strong-coupling analysis and quantum Monte Carlo simulations.

Findings

Small spin anisotropy enhances d-wave pairing similar to cuprates.

Increased anisotropy activates triplet p-wave pairing, leading to mixed d+p states.

Enhanced pairing strength suggests potential for higher superconducting transition temperatures.

Abstract

Altermagnets - collinear, zero-net-moment magnets with momentum-odd spin splitting protected by crystalline symmetries - offer a tunable route to suppress long-range antiferromagnetism while preserving strong short-range spin fluctuations. We show that this environment robustly stabilizes unconventional superconductivity and naturally produces mixed-symmetry pairing. Through a strong-coupling analysis of a spin-anisotropic Hubbard model, we derive an anisotropic t-J model where exchange interactions cooperatively enhance singlet d-wave pairing and promote triplet p-wave pairing. Our mean-field analysis reveals a pairing evolution driven by altermagnetic anisotropy: for small spin anisotropy, the d-wave channel is enhanced, closely resembling the dominant pairing symmetry in cuprate superconductors, which suggests that weak spin anisotropy may be an essential ingredient in realistic models of these materials. Constrained-path quantum Monte Carlo simulations confirm this picture, showing a regime where dominant d-wave correlations coexist with an emergent p-wave component near optimal doping. As spin anisotropy increases, strong C2 anisotropy and spin splitting activate the triplet channel, leading to a stable d+p mixed-pairing state. This synergistic state exhibits significantly enhanced overall pairing strength, suggesting the possibility of a higher superconducting transition temperature.