Variation of the Elastic Moduli at the Superconducting Transition

Abstract

Using an ultrasonic technique capable of measuring changes in the elastic moduli as small as one part in 107, the small modulus changes associated with then ormal-to-superconducting transition have been measured as a function of both temperature and magnetic field. Single-crystal specimens of the cubic metals Pb, V, Nb and Ta were used and all their elastic moduli measured so that changes in the bulk modulus and Debye θ could be computed. The results showed that changes in the zeropoint energy of the lattice can be far from negligible. Furthermore, the shear moduli are the most changed by the appearance of superconductivity.