paper

Non-rigid hole band in the extended t-J model

arXiv:cond-mat/9606043 · doi:10.1007/s002570050299

Abstract

The dispersion of one hole in an extended $t$ - $J$ model with additional hopping terms to second and third nearest neighbours and a frustration term in the exchange part has been investigated. Two methods, a Green's function projection technique describing a magnetic polaron of minimal size and the exact diagonalization of a $4 * 4$ lattice, have been applied, showing reasonable agreement among each other. Using additional hopping integrals which are characteristic for the CuO $_{2}$ plane in cuprates we find in the nonfrustrated case an isotropic minimum of the dispersion at the point $(I ¨ /2, I ¨ /2)$ in $k$ -space in good coincidence with recent angle-resolved photoemission results for the insulating compound Sr $_{2}$ CuO $_{2}$ Cl $_{2}$ . Including frustration or finite temperature which shall simulate the effect of doping, the dispersion is drastically changed such that a flat region and an extended saddle point may be observed between $(I ¨ /2, 0)$ and $(I ¨ , 0)$ in agreement with experimental results for the optimally doped cuprates.

14 pages, LaTeX, 6 figures on request, submitted to Zeitschrift fuer Physik