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Anomalous Enhancement of Upper Critical Field in Sr2RuO4 Thin Films

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 Added by Masaki Uchida
 Publication date 2019
  fields Physics
and research's language is English




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We report large enhancement of upper critical field Hc2 observed in superconducting Sr2RuO4 thin films. Through dimensional crossover approaching two dimensions, Hc2 except the in-plane field direction is dramatically enhanced compared to bulks, following a definite relation distinct from bulk one between Hc2 and the transition temperature. The anomalous enhancement of Hc2 is highly suggestive of important changes of the superconducting properties, possibly accompanied with rotation of the triplet d-vector. Our findings will become a crucial step to further explore exotic properties by employing Sr2RuO4 thin films.



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We report a highly unusual angular variation of the upper critical field (H_c2) in epitaxial superlattices CeCoIn_5(n)/YbCoIn_5(5), formed by alternating layers of n and a 5 unit-cell thick heavy-fermion superconductor CeCoIn_5 with a strong Pauli effect and normal metal YbCoIn_5, respectively. For the n=3 superlattice, H_{c2}(theta) changes smoothly as a function of the field angle theta. However, close to the superconducting transition temperature, H_{c2}(theta) exhibits a cusp near the parallel field (theta=0 deg). This cusp behavior disappears for n=4 and 5 superlattices. This sudden disappearance suggests the relative dominance of the orbital depairing effect in the n=3 superlattice, which may be due to the suppression of the Pauli effect in a system with local inversion symmetry breaking. Taking into account the temperature dependence of H_{c2}(theta) as well, our results suggest that some exotic superconducting states, including a helical superconducting state, might be realized at high magnetic fields.
155 - M. Uchida , M. Ide , H. Watanabe 2019
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