Non-rigid hole band in the extended t-J model
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 CuO2 plane in cuprates we find in the nonfrustrated case an isotropic minimum of the dispersion at the point (π/2,π/2) in k-space in good coincidence with recent angle-resolved photoemission results for the insulating compound Sr2CuO2Cl2. 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 (π/2,0) and (π,0) in agreement with experimental results for the optimally doped cuprates.
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