Finite temperature properties of the triangular lattice t-J model, applications to NaCoO
arXiv:cond-mat/0608005 · doi:10.1103/PhysRevB.74.245118
Abstract
We present a finite temperature () study of the t-J model on the two-dimensional triangular lattice for the negative hopping , as relevant for the electron-doped NaCoO (NCO). To understand several aspects of this system, we study the -dependent chemical potential, specific heat, magnetic susceptibility, and the dynamic Hall-coefficient across the entire doping range. We show systematically, how this simplest model for strongly correlated electrons describes a crossover as function of doping () from a Pauli-like weakly spin-correlated metal close to the band-limit (density ) to the Curie-Weiss metallic phase () with pronounced anti-ferromagnetic (AFM) correlations at low temperatures and Curie-Weiss type behavior in the high-temperature regime. Upon further reduction of the doping, a new energy scale, dominated by spin-interactions () emerges (apparent both in specific heat and susceptibility) and we identify an effective interaction , valid across the entire doping range. This is distinct from Anderson's formula, as we choose here , hence the opposite sign of the usual Nagaoka-ferromagnetic situation. This expression includes the subtle effect of weak kinetic AFM - as encountered in the infinitely correlated situation (). By explicit computation of the Kubo-formulae, we address the question of practical relevance of the high-frequency expression for the Hall coefficient . We hope to clarify some open questions concerning the applicability of the t-J model to real experimental situations through this study.