Control of the Mott transition by uniaxial pressure

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Application of pressure is known to induce a metallic state from an insulator or to enhance the transition temperature of a superconductor. In this project, we focus on the application of uniaxial pressure in order to amplify the effect or extract underlining mechanisms of an insulator-metal transition and exotic superconductivity. We improve the pressure apparatus for low-temperature experiments on brittle oxide crystals, as well as introduce a new apparatus capable of application of both compressional and tensile strain. Using layered ruthenium oxides, we found a strong in-plane anisotropy of the transition from a Mott insulator to a ferromagnetic metal. We also found that the superconducting transition of the ruthenium oxide Sr2RuO4 is enhanced by both compressional and tensile strain, thereby confirming the unusual behavior expected in a spin-triplet superconductor with aligned Cooper-pair angular momenta. These results demonstrate the usefulness of uniaxial pressure experiments.