arXiv:cond-mat/0409596 · Physical Review B
Gossamer superconductivity and antiferromagnetism in the t‐J‐U model
Feng Yuan, Qingshan Yuan, C. S. Ting
Abstract
The $d$-wave superconductivity (dSC) and antiferromagnetism are analytically studied in a renormalized mean-field theory for a two-dimensional $t\text{\penalty1000-\hskip0pt}J$ model plus an on-site repulsive Hubbard interaction $U$. The purpose of introducing the $U$ term is to partially impose the no-double-occupancy constraint by employing the Gutzwiller approximation. The phase diagrams as functions of doping $\ensuremath{\delta}$ and $U$ are studied. Using the standard value of $t∕J=3.0$ and in the large-$U$ limit, we show that the antiferromagnetic (AF) order emerges and coexists with the dSC in the underdoped region below the doping $\ensuremath{\delta}\ensuremath{\sim}0.1$. The dSC order parameter increases from zero as the doping increases and reaches a maximum near the optimal doping $\ensuremath{\delta}\ensuremath{\sim}0.15$. In the small-$U$ limit, only the dSC order survives while the AF order disappears. As $U$ increases up to a critical value, the AF order shows up and coexists with the dSC in the underdoped regime. At half-filling, the system is in the dSC state for small $U$ and becomes an AF insulator for large $U$. Within the present mean-field approach, we show that the ground-state energy of the coexistent state is always lower than that of the pure dSC state.