Evidence for the strain critical point in high Tc superconductors G. Bianconi M. Colapietro A. Pifferi N.L. Saini S. Agrestini A. Bianconi

A temperature-modula.ion technique was applied to investigate change in the chemical potential of niobium film at transition to the superconducting state. The first dorivative of the chemical potential is continuous at Tc: whereas the second derivative shows a jump.