“Glassy” low-temperature thermal properties in crystalline superconducting ZrNb alloys

The general characteristics of the specific heat and thermal conductivity of glasses have been found in a quenched single crystal of superconducting ZrNb(20%). From consideration of the diffusionless dynamical fluctuations between the ω and β atomic configurations of the ZrNb alloy, an atomic tunneling picture at low temperatures is proposed. The degree of these “glassy” properties decreases in a quenched ZrNb(8%) crystal and also in the annealed ZrNb(20%) sample. These changes are explained by the formation of large ω domains, which do not favor rapid tunneling motion.