O Efeito da Dopagem com Lacunas na Densidade de Energia Cinética de Condensação do supercondutor YBa2Cu3O7-δ

Abstract

Experimental results of DC magnetization were obtained and analyzed in order to investigate the effects of overdoping of charge carriers (p > 0,16) on the kinetic energy density of condensation of Cooper pairs (EK) of syngle crystals samples of Y1-xCaXBa2Cu3O7-δ (x ≤ 0,10). The single crystals used in this study were grown using the self-flux technique. They present an orthorhombic structure and display a superconducting transition temperature [TC (p)] consistent with that reported for these compounds in the literature.The behavior of EK as a function of T, μ0H (magnetic field intensity), and p was determined using the Superconductivity Virial Theorem (TVS) (EK = - M.B) on the magnetization data (M) obtained from the measurementes of DC magnetizatoin as a function of T, and μ0H, where the zero field cooled [MZFC (T)] and field cooled cooling [MZFC (T)] procedures were used. The profile presented by the EK versus T data proved to be commom for all the samples studied, in other words, they show a significant increase in the EK intensity as T decreases, from T < TC. The EK versus T behavior as a function of μ0H is physically justified by the superconducting order parameter concept and its dependence as a function of T and μ0H. On the other hand, the EK versus T data weak dependence as a function of μ0H, in the T ≥ TIRR (μ0H) range, observed for all samples surveyed, is associeated with the maintenance of the 3d vortex lattice behavior in the single crystals of Y1-xCaXBa2Cu3O7-δ (x ≤ 0,10). The identification of a maximum (p ~ 0,17) at EK and ρs data as a function of p, in the investigated single crystals, can be understood as the van Hove transition signiture, whose occurrence has been systematically observed in the DOS (density of states) behavior of differente HTSC (high temperature superconductors) at their overdoped state of p (p > 0,16). The manifestation of it probably is associated with the pseudogap (PG) state supression as compared to the superconducting phase (SC) in the overdoped regime of p along the T versus p diagram of the HTSC.