Carrier dispersion in the two-dimensional [formula omitted] model on a triangular lattice

Abstract

For the case of low concentration the carrier dispersion in the two-dimensional t – J model on a triangular lattice is investigated using Mori's projection operator technique. The dispersion depends strongly on the sign of the hopping constant t and on its ratio to the exchange constant J. For t > 0 minima of the band are located at the wave vectors Q = ( 2 π / 3 , 2 π / 3 ) and ( 4 π / 3 , 0 ) , while for t < 0 they are at α Q where the coefficient α < 1 decreases with increasing J / | t | . In the case t > 0 the width of the band decreases with increasing J / t without substantial change in its shape, while for t < 0 the band shape changes drastically with J / | t | . The obtained results are compared with experimental data in Na x CoO 2.