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

Generalized one-dimensionalt-Jmodels with longer-range spin exchange

J. Bonča, Peter Prelovšek

The behavior of holes in the one-dimensional (1D) t-J model differs substantially from the one in planar correlated systems. We show that within the 1D model one can recover some essential properties of 2D systems by including longer-range spin exchange. Be means of analytical calculations for the anisotropic exchange and the exact diagonalization of small systems, it is established that this generalization leads to the large mass enhancement for a single hole, to the hole binding at strongly reduced J/t, and to substantial changes in the phase diagram at electron densities n\ensuremath{\lesssim}1. It is shown that the longer spin exchange changes qualitatively the phase-separation line ${\mathit{J}}_{\mathit{c}}$ (n), which obtains an n dependence analogous to the 2D systems, i.e., opposite to the one in the 1D t-J model. The correlation exponent ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$ calculated in the Luttinger-liquid regime J ${\mathit{J}}_{\mathit{c}}$ (n) indicates also that the region of dominant pairing correlations can move even to J/t1.The behavior of holes in the one-dimensional (1D) t-J model differs substantially from the one in planar correlated systems. We show that within the 1D model one can recover some essential properties of 2D systems by including longer-range spin exchange. Be means of analytical calculations for the anisotropic exchange and the exact diagonalization of small systems, it is established that this generalization leads to the large mass enhancement for a single hole, to the hole binding at strongly reduced J/t, and to substantial changes in the phase diagram at electron densities n\ensuremath{\lesssim}1. It is shown that the longer spin exchange changes qualitatively the phase-separation line ${\mathit{J}}_{\mathit{c}}$(n), which obtains an n dependence analogous to the 2D systems, i.e., opposite to the one in the 1D t-J model. The correlation exponent ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$ calculated in the Luttinger-liquid regime J${\mathit{J}}_{\mathit{c}}$(n) indicates also that the region of dominant pairing correlations can move even to J/t1.

Physical review. B, Condensed matterSep 1, 19922 citations

Phase separation in the two-dimensional t–J model

C. T. Shih, Y. C. Chen, T. K. Lee

Physica C SuperconductivityNov 1, 20010 citations

Phase separation and three-site hopping in the two-dimensional t-J model

Elisa Ercolessi, P. Pieri, M. Roncaglia

arXiv:cond-mat/9701181Physics Letters ASep 1, 19976 citations

{\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.

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

(n), which obtains an n dependence analogous to the 2D systems, i.e., opposite to the one in the 1D t-J model. The correlation exponent ${\mathit{K}}_{\mathrm{\ensuremath{\rho}}}$ calculated in the Luttinger-liquid regime J

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

(n) indicates also that the region of dominant pairing correlations can move even to J/t1.