title: Anomalous upper critical field in CeCoIn5/YbCoIn5 superlattices with a Rashba-type heavy Fermion interface.
abstract: 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)(θ) changes smoothly as a function of the field angle θ. However, close to the superconducting transition temperature, H(c2)(θ) exhibits a cusp near the parallel field (θ=0°). 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)(θ) as well, our results suggest that some exotic superconducting states, including a helical superconducting state, might be realized at high magnetic fields.
authors.affiliation: Department of Physics, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: S K
authors.initials: SK
authors.lastname: Goh
authors.forename: Y
authors.initials: Y
authors.lastname: Mizukami
authors.forename: H
authors.initials: H
authors.lastname: Shishido
authors.forename: D
authors.initials: D
authors.lastname: Watanabe
authors.forename: S
authors.initials: S
authors.lastname: Yasumoto
authors.forename: M
authors.initials: M
authors.lastname: Shimozawa
authors.forename: M
authors.initials: M
authors.lastname: Yamashita
authors.forename: T
authors.initials: T
authors.lastname: Terashima
authors.forename: Y
authors.initials: Y
authors.lastname: Yanase
authors.forename: T
authors.initials: T
authors.lastname: Shibauchi
authors.forename: A I
authors.initials: AI
authors.lastname: Buzdin
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuda