Dimensional crossover in anisotropic Kondo lattices.

Dimensional crossover in the Kondo necklace model is analyzed using the bond-operator method at zero and finite temperatures. Explicit relations describing quasi-two-dimensional properties are obtained by asymptotically solving the resulting equations. The crossover from two dimensions (2d) to three dimensions (3d) is investigated, turning on the electronic hopping ([Formula: see text]) of conduction electrons between different planes. In order to give continuity to our analysis, both cases of crossover, quasi-three-dimensional (q3d) and quasi-one-dimensional (q1d), are also investigated. The phase diagram as a function of temperature T, [Formula: see text] and [Formula: see text], where [Formula: see text] is the hopping within the planes, is calculated. Unusual reentrant behavior in the temperature-dependent antiferromagnetic critical line is found close to two dimensions. Near the isotropic three-dimensional quantum critical point the critical line is described by a standard power law with a square root dependence on the distance to the quantum critical point.