In this work, after reviewing the theory of the elastic properties of Strontium ruthenate, an extension suitable to explain the sound speed experiments of Lupien et. al. \protect\cite{lup2} and Clifford et. al. \protect\cite{clif1} is carried out. It is found that the discontinuity in the elastic constant C66 gives unambiguous experimental evidence that the \sr superconducting order parameter Ψ has two components and shows a broken time-reversal symmetry state. A detailed study of the elastic behavior is performed by means of a phenomenological theory employing the Ginzburg-Landau formalism.
@article{arxiv.1812.06494,
title = {Symmetry Field Breaking Effects in Sr$_2$RuO$_4$},
author = {Pedro Contreras and Jose Florez and Rafael Almeida},
journal= {arXiv preprint arXiv:1812.06494},
year = {2018}
}