The role of transverse anisotropic elastic waves and Ehrenfest relationships in the superconducting state of the compound Sr$_2$RuO$_4$

Abstract

In this short review, some bulk threshold phenomena of the unconventional superconductivity in the strontium ruthenate compound (Sr2RuO4) are mentioned. Particularly, in Sr2RuO4, the Ehrenfest relations, the velocity propagation of the elastic field modes, and the ultrasound attenuation find a common point to study elastic anisotropic lattice field effects at the transition temperature (Tc) between the normal and the superconducting state. Ehrenfest relations are suitable for establishing a phase diagram of the Tc point according to symmetry consideration of the electrons pairs in unconventional superconductors. Further studies in this direction could turn into a new role for the spin polarization of the transverse phonon field and its interaction with the conduction electrons in anisotropic crystals with several conducting/superconducting bands such as Sr2RuO4.