Moment screening in the correlated Kondo lattice model

Abstract

The magnetic correlations, local moments and the susceptibility in the correlated two-dimensional (2D) Kondo lattice model at half-filling are investigated. We calculate their systematic dependence on the control parameters JK/t and U/t. An unbiased and reliable exact diagonalization approach for ground state properties as well as the finite temperature Lanczos method (FTLM) for specific heat and the uniform susceptibility are employed for small tiles on the square lattice. They lead to two major results: firstly, we show that the screened local moment exhibits non-monotonic behavior as a function of U for weak Kondo coupling JK. Secondly, the temperature dependence of the susceptibility obtained from the FTLM allows us to extract the dependence of the characteristic Kondo temperature scale T* on the correlation strength U. A monotonic increase of T* for small U is found, resolving the ambiguity of earlier investigations. In the large-U limit, the model is equivalent to the 2D Kondo necklace model with two types of localized spins. In this limit, the numerical results were compared with those of the analytical bond-operator method in the mean field treatment, and excellent agreement for the total paramagnetic moment was found, supporting the reliability of both methods.