We examine the influence of a staggered magnetic field on states involving a few holes in the one-dimensional t-J and Hubbard models. We apply exact diagonalizations of small systems, an analytical treatment of an anisotropic model, and a high-field perturbation expansion. Our results suggest that even modest staggered fields, h\ensuremath{\ll}t, induce the formation of bound hole pairs in a broad range of parameters, in particular for J/t1 in the t-J model and for U/t>1 in the Hubbard model. In the same regions, by studying the density-density correlations and the compressibility, we argue that many holes form a paired state and that phase separation does not occur.We examine the influence of a staggered magnetic field on states involving a few holes in the one-dimensional t-J and Hubbard models. We apply exact diagonalizations of small systems, an analytical treatment of an anisotropic model, and a high-field perturbation expansion. Our results suggest that even modest staggered fields, h\ensuremath{\ll}t, induce the formation of bound hole pairs in a broad range of parameters, in particular for J/t1 in the t-J model and for U/t>1 in the Hubbard model. In the same regions, by studying the density-density correlations and the compressibility, we argue that many holes form a paired state and that phase separation does not occur.

Physical Review LettersJul 20, 199216 citations

On the nature of pairing in the two-dimensional t–J model

Thomas Maier

Physica B Condensed MatterFeb 15, 20058 citations

Spin gap of the one-dimensional t–J model

Y. C. Chen

Physica C SuperconductivityNov 1, 20010 citations

Hole pairs in the one-dimensional Hubbard model in a staggered field

Janez Jaklič, Peter Prelovšek

The one-dimensional Hubbard model in a staggered magnetic field h, introduced recently to simulate planar correlated electronic systems, is studied within the unrestricted Hartree-Fock approximation. The emphasis is on solutions for a few holes added to the reference antiferromagnet. Both analytical results, available at U,ht, and numerical results confirm the polaronic character of a single-hole state for all U,h, while bipolarons (bound pairs of holes) are stable for 0U ${\mathit{U}}_{\mathit{c}}$ (h). Since under the same conditions we do not find any evidence for stable hole clusters and the phase separation, the latter regime remains a candidate for hole pairing.The one-dimensional Hubbard model in a staggered magnetic field h, introduced recently to simulate planar correlated electronic systems, is studied within the unrestricted Hartree-Fock approximation. The emphasis is on solutions for a few holes added to the reference antiferromagnet. Both analytical results, available at U,ht, and numerical results confirm the polaronic character of a single-hole state for all U,h, while bipolarons (bound pairs of holes) are stable for 0U${\mathit{U}}_{\mathit{c}}$(h). Since under the same conditions we do not find any evidence for stable hole clusters and the phase separation, the latter regime remains a candidate for hole pairing.

Physical review. B, Condensed matterMar 1, 19935 citations

One-dimensionalt-Jand Hubbard models in a staggered field

Peter Prelovšek, Igor Sega, J. Bonča +2 more

The influence of the staggered magnetic field h on properties of the one-dimensional t-J and Hubbard models with nearly half-filled bands are studied. Using the exact diagonalization method for small systems as well as analytical approaches possible in the anisotropic model and for h\ensuremath{\gg}t, we determine the phase diagram of the t-J-h model at low doping, which displays three different regimes: the phase with repelling holes for J ${\mathit{J}}_{\mathit{c}}$ , the phase with paired holes for ${\mathit{J}}_{\mathit{c}}$ J ${\mathit{J}}_{\mathit{s}}$ , and the phase separation for J> ${\mathit{J}}_{\mathit{s}}$ . Employing for h\ensuremath{\ne}0 the analogy with the universal behavior of one-dimensional interacting fermions within the Luther-Emery regime, we calculate the charge exponent ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$, which can be ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$>1 in the pairing regime, indicating dominant superconducting fluctuations. An analogous analysis, in particular the perturbation expansion in t/h, performed for the Hubbard t-U-h model shows a phase of stable hole pairs for U ${\mathit{U}}_{\mathit{c}}$ . Again ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$ seems to approach a nonuniversal value at half-filling.The influence of the staggered magnetic field h on properties of the one-dimensional t-J and Hubbard models with nearly half-filled bands are studied. Using the exact diagonalization method for small systems as well as analytical approaches possible in the anisotropic model and for h\ensuremath{\gg}t, we determine the phase diagram of the t-J-h model at low doping, which displays three different regimes: the phase with repelling holes for J${\mathit{J}}_{\mathit{c}}$, the phase with paired holes for ${\mathit{J}}_{\mathit{c}}$J${\mathit{J}}_{\mathit{s}}$, and the phase separation for J>${\mathit{J}}_{\mathit{s}}$. Employing for h\ensuremath{\ne}0 the analogy with the universal behavior of one-dimensional interacting fermions within the Luther-Emery regime, we calculate the charge exponent ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$, which can be ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$>1 in the pairing regime, indicating dominant superconducting fluctuations. An analogous analysis, in particular the perturbation expansion in t/h, performed for the Hubbard t-U-h model shows a phase of stable hole pairs for U${\mathit{U}}_{\mathit{c}}$. Again ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$ seems to approach a nonuniversal value at half-filling.

Physical review. B, Condensed matterMay 1, 19934 citations

{\mathit{U}}_{\mathit{c}}

(h). Since under the same conditions we do not find any evidence for stable hole clusters and the phase separation, the latter regime remains a candidate for hole pairing.

{\mathit{J}}_{\mathit{c}}

, the phase with paired holes for

{\mathit{J}}_{\mathit{c}}

{\mathit{J}}_{\mathit{s}}

, and the phase separation for J>

{\mathit{J}}_{\mathit{s}}

. Employing for h\ensuremath{\ne}0 the analogy with the universal behavior of one-dimensional interacting fermions within the Luther-Emery regime, we calculate the charge exponent ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$, which can be ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$>1 in the pairing regime, indicating dominant superconducting fluctuations. An analogous analysis, in particular the perturbation expansion in t/h, performed for the Hubbard t-U-h model shows a phase of stable hole pairs for U

{\mathit{U}}_{\mathit{c}}

. Again ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$ seems to approach a nonuniversal value at half-filling.