Eur. Phys. J. B 3, 427-435 (1998)
https://doi.org/10.1007/s100510050332

Charge correlations in the weakly doped t-J model calculated by projection technique

Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany

Corresponding author: ^a vojta@theory.phy.tu-dresden.de

Received: 10 July 1997
Revised: 19 March 1998
Accepted: 3 April 1998
Published online: 15 June 1998

Abstract

We study frequency- and wave-vector dependent charge correlations in weakly doped antiferromagnets using Mori-Zwanzig projection technique. The system is described by the two-dimensional t-J model. The ground state is expressed within a cumulant formalism which has been successfully applied to study magnetic properties of the weakly doped system. Within this approach the ground state contains independent spin-bag quasiparticles (magnetic polarons). We present results for the charge-density response function and for the optical conductivity at zero temperature for different values of t/J. They agree well with numerical results calculated by exact diagonalization techniques. The density response function for intermediate and large momenta shows a broad continuum on energy scales of order of several t whereas the optical conductivity for is dominated by low energy excitations (at 1.5-2J). We show that these weak-doping properties can be well understood by transitions between excited states of spin-bag quasiparticles.