Effects of Stress on Superconducting Sn, In, Tl, and Al

Abstract

Hydrostatic pressures of 0 to 100 atmos obtained with helium gas pressure, and of 1.9×${10}^3$ atmos obtained by an ice expansion bomb technique are used to measure the pressure displacement of critical temperature $T_c$. The coefficient ($\frac{\partial T_c}{\partial p}$) for Sn, In, Tl, and Al is -4.7±0.2, -4.0±0.2, +0.6±0.3, and -2.0±0.2 in units of ${10}^{-5\mathrm{}}$ °K/atmos, respectively. The temperature dependence of $R=\frac{{\left(\frac{\partial H_c}{\partial p}\right)}_T}{{\left(\frac{\partial H_c}{\partial p}\right)}_{T_c}}$ above 1°K is described by $R=0.61+0.029\mathrm{}{T}^2$ for Sn, and $R=0.77+0.020\mathrm{}{T}^2$ for In. This result is discussed in connection with the similarity principle, $\frac{H_0}{T_c}=\mathrm{constant}$. From an analysis combining stress and isotope effects, it is seen that $T_c$, or $H_c$, is more sensitive to volume changes, holding zero-point lattice vibration amplitude fixed, than to zero-point amplitude changes, holding $V$ fixed: ${\left(\frac{\partial H_c}{\partial \ln V}\right)}_{q^2}=5.5\mathrm{}\times {\left(\frac{\partial H_c}{\partial \ln q^2}\right)}_V$ for Sn. Zero-pressure critical field data are also presented for the subject metals.