2026/07/23 by A. V. Belov, A. N. Rubtsov, B. Krippa
#cond-mat.str-el
We consider the layered attractive Hubbard model with a moderate interaction strength at quarter filling. The Green's function, self-energy, and density of states are calculated for relatively large clusters using the fluctuating local field method within the approximation of vanishing effective interaction. The emergence of a pseudogap is demonstrated for the cluster system, and it is shown that integration over the fluctuating field is equivalent to the summation of zero-mode ladder diagrams above critical temperature. For the large layered system, a pseudogap in the density of states is obtained within a cluster scheme that treats the coupling between layers as a static U(1) symmetry-breaking field.