Superconductivity and Antiferromagnetism in an Extended Gutzwiller Approximation fort–JModel: Effect of Double-Occupancy Exclusion

Abstract

The ground state of two-dimensional t-J model including superconductivity and antiferromagnetism is studied using a new type of analytic estimation of the effect of strong correlation. The method is an extension of the Gutzwiller approximation which gives renormalization of parameters, t and J, due to the Gutzwiller projection operator excluding double occupancies. It is shown that the essential point of the renormalization is its dependence on the expectation values of superconductivity and antiferromagnetic moment. In special the renormalization factor is anisotropic in spin space, which leads to a reliable estimate of antiferromagnetic order parameters in the phase diagram, in contrast to the conventional slave-boson mean-field theory. The obtained phase diagram shows the coexistence of antiferromagnetism and d x 2 Ày 2 -wave superconductivity for the doping rate, , less than 10%. At half-filling, the renormalization of the J-term represents some aspects of quantum spin nature. For the finite doping case, there are two kinds of superconducting order parameters. The variational order parameter of the dwave superconductivity increases as the doping rate decreases, which will correspond to the experimentally observed superconducting gap. In contrast, the actual expectation value of superconducting order parameter is proportional to in underdoped region and has a maximum near ¼ 0:11, which probably determines T c . We also speculate that the ground-state antiferromagnetic order, being destroyed at finite temperatures, gives the energy and temperature scale of the pseudogap. Applications to the inhomogeneous systems such as the vortex state and stripe state are discussed.

Antiferromagnetism in two-dimensionalt−Jmodel: A pseudospin representation

“…Our method yields reasonable value of the critical doping δ c , at which the antiferromagnetic long-range order disappears, in good agreement with the numerical calculations 16,17,18,19,20 .…”

“…In order to calculate the staggered magnetization of the model, we employ the many-body Green's function method developed by Fröbrich and Kuntz 15 . Unlike the slave particle methods, we show that the critical doping δ c for the disappearance of antiferromagnetic long-range order is in good agreement with the numerical calculations 16,17,18,19,20 . This paper is organized as follows.…”

Phase competition and anomalous thermal evolution in high-temperature superconductors

“…For example, the resulting antiferromagnetic state extends to high doping density. It can be improved by taking the feedback effect of the order parameters into account [64,87]. The modified Gutzwiller factors are…”

Origin of the heavy fermion behavior in Ca2−xSrxRuO4Arakawa1, Ogata2 2012Phys. Rev. BSelf Cite81220View full textAdd to dashboardCite

“…To calculate the expectation values, we use the GA [22][23][24][25][26] in which the dependence of the Slater determinants on the configurations is neglected. For example, the square of the Slater determinant, [det U 1↑ ({r…”