Altermagnetism-driven FFLO superconductivity in finite-filling 2D lattices

We systematically investigate the emergence of finite-momentum Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductivity in a square lattice Hubbard model with finite filling, driven by either $$d_{xy}$$ -wave or $$d_{x^{2}-y^{2}}$$ -wave altermagnetic order in the presence of on-site $$s$$ -wave attractive interactions. Our study combines mean-field calculation in the superconducting phase with pairing instability analysis of the normal state, incorporating the next-nearest-neighbor hopping in the single-particle dispersion relation. We demonstrate that the two types of altermagnetism have markedly different impacts on the stabilization of FFLO states. Specifically, $$d_{xy}$$ -wave altermagnetism supports FFLO superconductivity over a broad parameter regime at low fillings, whereas $$d_{x^{2}-y^{2}}$$ -wave altermagnetism only induces FFLO pairing in a narrow range at high fillings. Furthermore, we find that the presence of a Van Hove singularity in the density of states tends to suppress FFLO superconductivity. These findings may provide guidance for experimental exploration of altermagnetism-induced FFLO states in real materials with more complex electronic structures.