Sur ce site

Sur le Web du CNRS

Accueil du site > Publications > Publications 2006 > Bond-order-modulated flux-phase of the t-J model on a square lattice

Bond-order-modulated flux-phase of the t-J model on a square lattice

Cédric Weber, Didier Poilblanc, Sylvain Capponi, Frédéric Mila, Cyril Jaudet

par Webmaster - 19 novembre 2004

Motivated by the observation of inhomogeneous patterns in some high-T_c cuprate compounds, several variational Gutzwiller-projected wave-functions with built-in charge and bond order parameters are proposed for the extended t-J-V model on the square lattice at low doping. First, following a recent Gutzwiller-projected mean-field approach by one of us (Phys. Rev. B. 72, 060508(R) (2005)), we investigate, as a function of doping and Coulomb repulsion, the relative stability of a wide variety of modulated structures with square unit cells of size 2\times 2, \sqrt{8}\times\sqrt{8}, 4\times 4 and \sqrt{32}\times\sqrt{32}. It is found that the 4\times 4 bond-order wave-function with staggered flux pattern (and small charge and spin current density wave) is a remarkable competitive candidate for hole doping around 1/8 in agreement with STM observations in the under-doped regime of some cuprates. This wave-function is then optimized accurately and its properties studied extensively using an approximation-free variational Monte Carlo scheme. Moreover, we find that under increasing the Coulomb repulsion, the d-wave superconducting RVB wave-function is rapidly destabilized with respect to the the 4\times 4 bond-order wave-function. The stability of the bond-modulated wave-function is connected to a gain of Coulomb and exchange energies. We suggest that such ordering patterns could be dynamical or could spontaneously appear in the vicinity of an impurity or a vortex in the mixed phase of the cuprates. Finally, we consider also a commensurate flux phase, but this wave-function turns out not to be competitive because of its rather poor kinetic energy. However, we find it has very competitive exchange and Coulomb energies.