Piezoelectric-based uniaxial pressure devices have become an important tool for investigating correlated electron systems. In SrRuO, a Van Hove singularity can be tuned to the Fermi level, which more than doubles the superconducting critical temperature. With a new style of pressure device, the authors have measured here the stress at which this occurs with high accuracy, and the result now gives an unmistakable discrepancy with predictions from noninteracting electronic structure calculations. With this knowledge, they put constraints on the interaction parameters, improving our understanding of both the pressurized and ambient-pressure properties of SrRuO.
