One-hole motion in the two-dimensional frustrated t-J model

The influence of a frustration term in the exchange part of the t-J model onto the dispersion relation of one hole has been investigated. We have chosen two independent methods, namely, a variational ansatz which describes a magnetic polaron of minimal size and the exact diagonalization method of a 4x4 lattice. It has been found that the frustration shifts the minimum from the point (pi/2, pi/2) to the point (0,pi) in k space. It has also been shown that the frustration term alone does not lead to the correct, experimentally observed Aat dispersion region around (0,pi). A better agreement with the observed, extended saddle point singularity may be obtained by simulating the decrease of spin correlations due to a finite temperature.