Exploring Superconductivity in Chiral Structured AuBe

Abstract

AuBe is a noncentrosymmetric superconductor with the B20 FeSi-type structure. Noncentrosymmetric superconductors are expected to give rise to unconventional superconductivity due to spin orbit coupling and a mixed spin-singlet, spin-triplet state. The B20 structure of AuBe is particularly interesting since this is one of the only known crystal structures for bulk magnetic skyrmions in materials such as MnSi and Cu2OSeO3. The superconducting state was characterized by specific heat, dc magnetization, ac susceptibility, and resistivity. Specific heat revealed AuBe to host an isotropic gap characteristic of predominantly s-wave spin-singlet pairing in the weak coupling limit. Magnetization and susceptibility measurements revealed a critical temperature of 3.2 K and a crossover from Type I to Type II superconductivity at approximately 1.2 K. Resistivity characterization of the superconducting transition revealed significantly higher critical fields at lower temperature. The robust critical fields as measured in the resistivity are attributed to either a surface superconducting state that is robust against the deposition of magnetic thin films, or a filamentary superconductivity at twin boundaries enhanced by spin orbit coupling.