Effect of Stress on the Superconducting Transition Temperature of SrTiO3

The superconducting transition temperatures of several specimens of reduced SrTiO3 and of Nb-doped SrTiO3 have been investigated as functions of hydrostatic and uniaxial compressive stresses up to 1.8 kbars. Decreases in T-c as large as 0.12 K have been observed in specimens under hydrostatic pressure. Because of the low T-c and small compressibility of SrTiO3, Delta(ln T-c)/Delta P and Delta(ln T-c)/Delta(ln V) are orders of magnitude greater than the corresponding effects in elemental superconductors. The effect of uniaxial stress on T-c varied with the direction of stress. Compression along a [111] direction caused large decreases in T-c, while both small increases and small decreases in T-c have been observed for [100] compression. It is believed that the present results reveal the presence of a sensitive volume dependence in one or more of the parameters important to superconductivity in SrTiO3, and that no significant electron-transfer effects occurred in the range of stresses of this experiment.