Two-dimensional extended Hubbard model at half-filling

We consider the extended Hubbard model on a two-dimensional square lattice at half-filling. The is investigated using strong coupling diagram technique. sum infinite series of ladder diagrams allowing for full-scale charge and spin fluctuations actual short-range antiferromagnetic order nonzero temperatures. In agreement with earlier results, we find first-order phase transition in subsystem occurring $v=v_c\gtrsim U/4$ $v$ $U$ intersite on-site Coulomb repulsion constants. reveals itself an abrupt sign change sharp maximum zero-frequency susceptibility corner Brillouin. States arising have alternating deviations electron occupations from mean value neighboring sites. Due to fluctuations, these occupation order. For considered parameters, such behavior found $U\lesssim5t$ $t$ hopping constant. insulating case $U\gtrsim 6t$, which not observed, continuous growth Mott gap $v$. evolution density states increasing also considered.