Low-temperature specific heat of Bi₂Sr₂CaCu₂O₈: Comparison with some other layered oxides

The specific heat of crystals of superconducting Bi2Sr2CaCu2O8 in the range 2-5 K varies as γT + βT3, with γ = 7(2) mJ mol-1 K-2. A slight upturn in C T is observed below 2 K. The low-temperature specific heats of the semiconducting copper oxide layer compound Sr14Cu24O41 and the insulating sheet silicate KAl3Si3O10(OH)2 (muscovite mica) are qualitatively similar, with γ = 100(5) mJ mol-1 K-2 and γ = 25(5) mJ mol-1 K-2 respectively. We infer that the linear term is not connected with superconductivity; a likely origin is the localized electronic states associated with oxygen vacancies. © 1989.