Two-dimensional t-J model at moderate doping

TL;DR

This study investigates the spectral and magnetic properties of the two-dimensional t-J model at moderate doping levels, revealing insights into pseudogap formation, Fermi surface evolution, and magnetic correlations relevant to cuprate superconductors.

Contribution

The paper introduces a method that preserves spin rotation symmetry without preset magnetic order, providing new insights into the normal state properties of the 2D t-J model at finite doping.

Findings

Homogeneous solutions indicate no phase separation due to strong correlations.

Identification of nearly equidistant maxima in the spectral function related to hole vibrations.

Observation of a pseudogap near (0,π) and (π,0) in the hole spectrum.

Abstract

Using the method which retains the rotation symmetry of spin components in the paramagnetic state and has no preset magnetic ordering, spectral and magnetic properties of the two-dimensional t-J model in the normal state are investigated for the ranges of hole concentrations 0 <= x <= 0.16 and temperatures 0.01t <= T <= 0.2t. The used hopping t and exchange J parameters of the model correspond to hole-doped cuprates. The obtained solutions are homogeneous which indicates that stripes and other types of phase separation are not connected with the strong electron correlations described by the model. A series of nearly equidistant maxima in the hole spectral function calculated for low T and x is connected with hole vibrations in the region of the perturbed short-range antiferromagnetic order. The hole spectrum has a pseudogap in the vicinity of (0,\pi) and (\pi,0). For x \approx 0.05 the shape of the hole Fermi surface is transformed from four small ellipses around (\pm\pi/2,\pm\pi/2) to two large rhombuses centered at (0,0) and (\pi,\pi). The calculated temperature and concentration dependencies of the spin correlation length and the magnetic susceptibility are close to those observed in cuprate perovskites. These results offer explanations for the observed scaling of the static uniform susceptibility and for the changes in the spin-lattice relaxation and spin-echo decay rates in terms of the temperature and doping variations in the spin excitation spectrum of the model.