Despite significant achievements in characterizing the properties of Sr2RuO4 over the last three decades, the precise nature of its electronic ground state is still unresolved. In this work, we provide a missing piece of the puzzle by uncovering evidence of electronic nematic order in the normal state of Sr2RuO4, revealed by ultrafast time-resolved optical dichroism measurements of uniaxially strained thin films. This nematic order, whose domains are aligned by the strain, spontaneously breaks the four-fold rotational symmetry of the crystal. The temperature dependence of the dichroism resembles an Ising-like order parameter, and optical pumping induces a coherent oscillation of its amplitude mode. A microscopic model of intra-unit-cell nematic order is presented, highlighting the importance of Coulomb repulsion between neighboring oxygen p-orbitals. The existence of electronic nematic order in the normal state of Sr2RuO4 may have consequences for the form and mechanism of superconductivity in this material.
@article{arxiv.2304.02586,
title = {Electronic nematic order in the normal state of strontium ruthenate},
author = {Ryan Russell and Hari P. Nair and Kyle M. Shen and Darrell G. Schlom and John W. Harter},
journal= {arXiv preprint arXiv:2304.02586},
year = {2023}
}