We investigate the competition between superconductivity (SC) and charge density wave (CDW) under a time-dependent periodic field in the attractive Hubbard model. By employing the time-dependent exact diagonalization method, we show that the driving frequency and amplitude of the external field can control the enhancement of either the superconducting pair or the CDW correlation in the system, for which SC and CDW are degenerate in the ground state of the half-filled attractive Hubbard model in the absence of the field. In the strong-coupling limit of the attractive Hubbard interaction, the controllability is characterized by the anisotropic interaction of the effective model. The anisotropy is induced by the external field and lifts the degeneracy of SC and CDW. We find that the enhancement or suppression of the superconducting pair and CDW correlations in the periodically driven attractive Hubbard model can be well interpreted by the quench dynamics of the effective model derived in the strong-coupling limit.
Abstract The issue of whether d -wave superconductivity (SC) occurs in the square-lattice Hubbard model with U of order of the bandwidth has been one of the most debated issues to emerge from the study of high temperature SC. Here, we report variational results on eight-leg cylinders with next-nearest-neighbor hopping in the range
−0.5t≤t′≤0.25t − 0.5 t ≤ t ′ ≤ 0.25 t with U = 8 t and 12 t and doped hole concentrations δ = 1/12 and 1/8. For
t′≤0 t ′ ≤ 0 , the ground-state appears to be a charge-density wave (CDW) of one sort or another with SC correlations that are extremely short-ranged. In contrast, in some cases, the local magnetic order has a correlation length greater than half the cylinder width - suggestive that magnetic order might also arise in the 2D limit. For
t′>0 t ′ > 0 , our results depend more strongly on boundary conditions (periodic vs antiperiodic), making it still harder to correctly guess whether SC or CDW correlations dominate in the 2D limit. These results were obtained employing matrix-product states with bond dimensions large enough that energy differences as small as 10 −3 t per site can be resolved.
We investigate the superuid properties of d-wave pairing symmetry within the Extended Hubbard Model (EHM) in a magnetic eld.We analyze the temperature and magnetic eld dependencies of the order parameter.We nd that in the two-dimensional case, the spatially homogeneous spin polarized superuidity (SC (P ̸ = 0)) is stable in the weak coupling limit, at T = 0, as opposed to the s-wave pairing symmetry case in 2D.We construct the ground state phase diagrams both for xed chemical potential and electron concentration.Furthermore, we obtain the temperature vs. magnetic eld and temperature vs. spin polarization phase diagrams.