Abstract

The influence of high hydrostatic pressure on the transition temperatureT _c has been investigated for the superconductors of group Va of the Periodic Table up to 45 kbars. Results obtained for tantalum, showing a negative pressure effectdT _c /dp, are in good agreement with earlier observations. For vanadium and niobium, however,dT _c /dp is found to be positive with an initial slope 1.76 · 10⁻⁵ °K/bar and 1.2 · 10⁻⁵ °K/bar respectively. In addition, a very strong influence onT _c anddT _c /dp of lattice defects produced by plastic deformation at low temperatures has been observed for V and Nb. Comparatively small increases of the residual resistance yield an increase ofT _c and a pronounced minimum in theT _c -p-dependence for both metals.

The results are discussed with regard to possible influence of pressure on the density of states and the Debye temperature.