Superconducting State in LaNiGa2 and Sr2RuO4 Single Crystals Investigated with μSR

Synopsis

In this work, transverse-field (TF) muon spin rotation (μSR) technique was employed to determine the in-plane magnetic penetration depth λac in high-quality LaNiGa2 single crystals. The temperature dependence of the superfluid density inferred from measurements of λac(T) is well described by a two-band model with strong interband coupling, supporting a proposed internally antisymmetric, nonunitary spin-triplet state for this superconductor. This thesis also revisits two TF-μSR studies of Sr2RuO4 that show different behaviors for the limiting low-T temperature dependence of the in-plane magnetic penetration depth λaband hence reach different conclusions regarding the superconducting gap structure. Here it is shown through the application of a common data analysis method that both studies are consistent with a low-temperature λab ∝ T2 dependence, and are in agreement with Meissner-state measurements of Δλab(T) = λab(T) − λab(0) obtained by other techniques. In addition, the magnetic field profile B(r) in Sr2RuO4 is shown to be abnormal, introducing a new constraint on the possible superconducting order parameters of Sr2RuO4.

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