Resistivity in the Vicinity of a van Hove Singularity: Sr2RuO4 under Uniaxial Pressure

We report the results of a combined study of the normal-state resistivity and superconducting transition temperature T-c of the unconventional superconductor Sr2RuO4 under uniaxial pressure. There is strong evidence that, as well as driving T-c through a maximum at similar to 3.5 K, compressive strains epsilon of nearly 1% along the crystallographic [100] axis drive the gamma Fermi surface sheet through a van Hove singularity, changing the temperature dependence of the resistivity from T-2 above, and below the transition region to T-1.5 within it. This occurs in extremely pure single-crystals in which the impurity contribution to the resistivity is < 100 n Omega cm, so our study also highlights the potential of uniaxial pressure as a more general probe of this class of physics in clean systems.