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The two-leg t-J ladder: A mean-field description

Y. L. Lee·Y. W. Lee·C. -Y. Mou·Z. Y. Weng
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Abstract

Two-leg t-J ladders are investigated in the framework of a combination of the phase string formulation and bond-operator representation. We develope a mean-field theory in the strong rung interaction regime, i.e. $J_{\perp}\gg J, t$, which provides a unified description of the undoped insulating phase and the low doping phase --- the so-called C1S0 phase. Both of them are characterized by the resonating-valence-bond (RVB) order parameter, with gap opened up in all spin excitations. The ground state of the doped phase is intrinsically a superconductor with a d-wave symmetry, which is driven by the RVB correlations. The ground-state energy is in good agreement with numerical results. Phase separation is shown to occur beyond some critical value of J/t for given doping concentration. We also show that the spin gap in the doped phase is determined by quasi-particle-like excitations. The local structure of hole pairs as well as the spectra of various spin and charge modes are analyzed in comparison with other approaches.

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Y. L. Lee, Y. W. Lee, C. -Y. Mou, Z. Y. Weng. 1999-03-03. The two-leg t-J ladder: A mean-field description. https://doi.org/10.1103/physrevb.60.13418

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