Multiple Current Enhancement Regimes and Interaction Induced Re-entrant Transport in a Quasiperiodic Hubbard Ring with Antiferromagnetic Order

Abstract

We investigate persistent charge and spin currents in a one-dimensional quantum ring threaded by an Aharonov-Bohm (AB) flux, considering generalized Aubry-André-Harper (AAH) modulation with staggered onsite energies and antiferromagnetic (AFM) ordering in both the noninteracting and interacting regimes, with the latter treated using a self-consistent Hartree-Fock mean field theory (MFT). At half filling, two distinct current-enhancement peaks emerge as the modulation strength increases, with quasiperiodic hopping modulation playing a crucial role in establishing the two-peak structure within a restricted parameter regime. Spin-resolved bond-current profiles reveal a switch in the dominant spin contribution between the two peaks, while the inverse participation ratio (IPR) and flux-dependent spin-resolved ground-state energies provide complementary insights into the spatial characteristics of the eigenstates and their spin-dependent flux sensitivity. At quarter filling, the spin current exhibits a single enhancement peak, in contrast to the two-peak response observed at half filling. The Hubbard interaction affects the two half-filled peaks differently: it suppresses the primary peak, whereas the secondary peak exhibits a nonmonotonic, re-entrant response, with the current recovering at finite interaction strength. The interacting results are further characterized through the Drude weight, and comparisons with exact diagonalization (ED) and density-matrix renormalization group (DMRG) calculations for a finite half-filled system support the reliability of the MFT description. Our findings elucidate how quasiperiodic modulation, AFM order, band filling, and electronic correlations collectively govern the magnitude and spin-resolved character of persistent currents, giving rise to multiple enhancement regimes and interaction-induced re-entrant behavior.