Constraints on a split superconducting transition under uniaxial strain in Sr2RuO4 from scanning SQUID microscopy

Abstract

More than two decades after the discovery of superconductivity in Sr2RuO4, it is still unclear whether the order parameter has a single component or two degenerate components. For any two-component scenario, application of uniaxial strain is expected to lift the degeneracy, generating two distinct phase transitions. The presence of a second (lower-temperature) transition may be observable by probes that are sensitive to changes in the London penetration depth, λ, as a function of temperature, T. Here, we use scanning SQUID microscopy combined with a uniaxial strain device to test for a second transition under strain. We only observe a single transition. Within the temperature range where a second transition has been suggested by μSR measurements [Grinenko et al., Nat. Phys. 17, 748 (2021)], we further place a tight upper bound of less than 1% on the change in the zero temperature superfluid density ns∝λ−2(0) due to a second transition, suggesting that such a transition does not occur. These results constrain theories of the order parameter in Sr2RuO4.

Source-reported materials — not catalogue approval

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