Electronic nematic order in the normal state of strontium ruthenate

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 talk, I will detail our work 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. The existence of electronic nematic order in the normal state of Sr₂RuO₄ may have consequences for the form and mechanism of unconventional superconductivity in this material.