Abstract
The effect of high hydrostatic pressure on the magnetic field and temperature dependence of the attenuation of a longitudinal ultrasonic wave propagated along the ⟨100⟩ direction in superconducting has been investigated. The magnetic field dependence of the attenuation suggests the vertical character of the nodes in the superconducting gap. Application of pressure causes a decrease of the critical temperature and critical magnetic field ; the width of the transition under pressure increases. The dependence of on was found to be linear, in contrast to the quadratic one for . The slope has a universal character; its value does not depend on the physical factor causing reduction of , regardless if it is pressure or impurities. The observed effects demonstrate that the pressure application induces an increase in the electron-electron interaction. We show that this increase can be described in terms of a changing electron relaxation time, as in the case of impurities.
- Received 15 December 2007
DOI:https://doi.org/10.1103/PhysRevB.77.052502
©2008 American Physical Society