Violation of the Wiedemann-Franz law as an evidence of the pseudogap in the iron-based superconductor Ba(Fe1-xCox)2As2

Abstract

Longitudinal and transverse transport coefficients of the Ba(Fe1-xCox)2As2 single crystals with x = 0, 0.045, 0.06 and 0.244 were measured in the temperature range 1.4 - 300 K and in magnetic fields up to 12.5 T. The resulting data were used to determine the temperature dependence of the Hall Lorenz number (Lxy) and its evolution with doping. Lxy is defined by the electronic contributions to the thermal and electrical conductivities and it is found to differ from its canonical behavior. This shows the emergence of a pseudogap in samples at intermediate doping.