Superconducting Transition in Zinc and Gallium

The superconducting transitions of Ga and Zn have been studied to compare the supercooling of these elements with that shown by Al under similar conditions. Both Ga and Zn show considerably less tendency to supercool than Al despite their lower critical temperatures. The measurements also provide values of $T_c$ and ${\left(\frac{d{H}_c}{\mathrm{dT}}\right)}_{T_c}$ for Ga and Zn for comparison with recently reported calorimetric data. Attention is called to the fact that discrepancies still exist between direct calorimetric determination of the specific heat discontinuity at the critical temperature and the value deduced thermodynamically from critical field data. It is shown that such discrepancies are conspicuously worse among the elements Zn, Ga, and Al than for the elements of higher $T_c$ (In, Sn, Ta, and Pb) where agreement is within experimental error.