In order to identify the most favorable situation for superconductivity in the repulsive single-band Hubbard model, we have studied instabilities for d-wave pairing mediated by antiferromagnetic spin fluctuations and p-wave pairing mediated by ferromagnetic fluctuations with the fluctuation exchange approximation in both two dimensions and three dimensions. By systematically varying the band filling and band structure we have shown that (i) d pairing is stronger in two dimensions than in three dimensions and (ii) p pairing is much weaker than d pairing.In order to identify the most favorable situation for superconductivity in the repulsive single-band Hubbard model, we have studied instabilities for d-wave pairing mediated by antiferromagnetic spin fluctuations and p-wave pairing mediated by ferromagnetic fluctuations with the fluctuation exchange approximation in both two dimensions and three dimensions. By systematically varying the band filling and band structure we have shown that (i) d pairing is stronger in two dimensions than in three dimensions and (ii) p pairing is much weaker than d pairing.

arXiv:cond-mat/9909119Physical review. B, Condensed matterDec 1, 199976 citations

Charge fluctuations in the 2D Hubbard model

R. Citro, S. Di Matteo, M. Marinaro

Physica C SuperconductivityNov 1, 20001 citation

Néel order, ring exchange, and charge fluctuations in the half-filled Hubbard model

Jean-Yves P. Delannoy, Michel J. P. Gingras, P. C. W. Holdsworth +1 more

We investigate the ground state properties of the two-dimensional half-filled one band Hubbard model in the strong (large- $U$ ) to intermediate coupling limit (i.e., away from the strict Heisenberg limit) using an effective spin-only low-energy theory that includes nearest-neighbor exchange, ring exchange, and all other spin interactions to order $t{(t∕U)}^{3}$ . We show that the operator for the staggered magnetization, transformed for use in the effective theory, differs from that for the order parameter of the spin model by a renormalization factor accounting for the increased charge fluctuations as $t∕U$ is increased from the $t∕U\ensuremath{\rightarrow}0$ Heisenberg limit. These charge fluctuations lead to an increase of the quantum fluctuations over and above those for an $S=1∕2$ antiferromagnet. The renormalization factor ensures that the zero temperature staggered moment for the Hubbard model is a monotonously decreasing function of $t∕U$ , despite the fact that the moment of the spin Hamiltonian, which depends on transverse spin fluctuations only, in an increasing function of $t∕U$ . We also comment on quantitative aspects of the $t∕U$ and $1∕S$ expansions.We investigate the ground state properties of the two-dimensional half-filled one band Hubbard model in the strong (large-$U$) to intermediate coupling limit (i.e., away from the strict Heisenberg limit) using an effective spin-only low-energy theory that includes nearest-neighbor exchange, ring exchange, and all other spin interactions to order $t{(t∕U)}^{3}$. We show that the operator for the staggered magnetization, transformed for use in the effective theory, differs from that for the order parameter of the spin model by a renormalization factor accounting for the increased charge fluctuations as $t∕U$ is increased from the $t∕U\ensuremath{\rightarrow}0$ Heisenberg limit. These charge fluctuations lead to an increase of the quantum fluctuations over and above those for an $S=1∕2$ antiferromagnet. The renormalization factor ensures that the zero temperature staggered moment for the Hubbard model is a monotonously decreasing function of $t∕U$, despite the fact that the moment of the spin Hamiltonian, which depends on transverse spin fluctuations only, in an increasing function of $t∕U$. We also comment on quantitative aspects of the $t∕U$ and $1∕S$ expansions.

arXiv:cond-mat/0412033Physical Review BSep 16, 200553 citations

Large charge fluctuation in the one-dimensional Hubbard model

Norio Kawakami, Ayao Okiji

Physica B Condensed MatterApr 1, 19901 citation

We investigate the ground state properties of the two-dimensional half-filled one band Hubbard model in the strong (large-

U

) to intermediate coupling limit (i.e., away from the strict Heisenberg limit) using an effective spin-only low-energy theory that includes nearest-neighbor exchange, ring exchange, and all other spin interactions to order

t{(t∕U)}^{3}

. We show that the operator for the staggered magnetization, transformed for use in the effective theory, differs from that for the order parameter of the spin model by a renormalization factor accounting for the increased charge fluctuations as

t∕U

is increased from the $t∕U\ensuremath{\rightarrow}0$ Heisenberg limit. These charge fluctuations lead to an increase of the quantum fluctuations over and above those for an

S=1∕2

antiferromagnet. The renormalization factor ensures that the zero temperature staggered moment for the Hubbard model is a monotonously decreasing function of

t∕U

, despite the fact that the moment of the spin Hamiltonian, which depends on transverse spin fluctuations only, in an increasing function of

t∕U

. We also comment on quantitative aspects of the

t∕U

and

1∕S

expansions.