This article is cited in 3 papers

Cluster perturbation theory for the Hubbard model: the pinning of chemical potential

Sergey V. Nikolaev^a, Sergey G. Ovchinnikov<sup>b

a</sup> Omsk State University, Omsk, Russia
^b Siberian Federal University, Krasnoyarsk, Russia

Abstract: In this paper we study the single-band two-dimensional Hubbard model in the framework of the cluster perturbation theory. Consideration is limited to nearest-neighbor approximation. The original two-dimensional square lattice is divided into clusters of $2\times2$, forming a square superlattice. The complete set of eigenvectors and eigenvalues of a single cluster is determined by exact diagonalization method. On this basis, we construct X-operators, through which overrides the Hamiltonian of the problem. The spectral function is computed within the Hubbard-I approximation. This function allows to explore the distribution of spectral weight of the quasiparticles in the Hubbard subbands. The effect of the in-gap states at the pinning of the chemical potential at low concentrations of holes is explored.

Keywords: cluster perturbation theory, Hubbard model, strong electron correlation, exact diagonalization, X-operators, density of states.

UDC: 53.01+538.955+538.915

Received: 18.07.2010
Received in revised form: 25.10.2010
Accepted: 10.12.2010