Enhanced density of states in Li(Fe1−xCox)As single crystals near x = 0.06 as implied by transport properties

Abstract

Single crystals of Li(Fe1−xCox)As (x=0.00, 0.02, 0.04, 0.06, 0.08 and 0.1) were grown by the Sn-flux method and their resistivity behaviors were investigated. As the Co concentration x increased, the superconducting transition temperature Tc as well as the residual resistivity ratio systematically decreased, indicating a monotonic doping of electron carriers. Upon the analysis of the Fermi-liquid behavior of the resistivity and by using the Kadowaki–Woods relation, the T2 coefficient of the resistivity A and the Sommerfeld coefficient γN were found to increase abruptly near x=0.06. This is the point in the phase diagram at which the density of states at the Fermi energy (proportional to γN) is expected to be enhanced due to the collapse of the small hole-pockets. This result suggests that the Li(Fe1−xCox)As series at least up to x=0.08 remain as compensated metals and their transport properties are determined by multi-band effects.