Effect of pressure on the superconducting transition of lead

Abstract

The effect of hydrostatic pressures up to 300 atmospheres on the critical magnetic field of superconducting lead has been measured at a temperature slightly below the critical temperature. The pressures were applied using helium gas as the pressure transmitting fluid. The critical fields of the pressurized specimen and a zero-pressure comparison specimen were measured alternately using a sensitive d.c. ballistic method. The pressure-induced critical field difference ΛH c was found to vary linearly with pressure with a slope (δ H c /δ p) T = −9.60 ± 0.11 × 10 −9 gauss/ dyne cm −2 at about 7.09° K. The factors influencing the magnitude of the pressure shift are discussed on the basis of the Bardeen theory. The pressure shift for lead, unlike that for other super-conductors which have been measured, is about the same as that which is estimated from a consideration of zero-point vibration-amplitude changes only.