Interface-induced superconductivity at ∼25 K at ambient pressure in undoped CaFe ₂ As ₂ single crystals

Significance One of the major goals for scientists in the field of superconductivity and materials science has been to obtain superconductors with higher critical temperatures (T c ). One way that has long been proposed to achieve enhanced T c s is to take advantage of artificially or naturally assembled interfaces. The present work clearly demonstrates that high-T c superconductivity in the well-known nonsuperconducting compound CaFe 2 As 2 can be induced by antiferromagnetic/metallic layer stacking and provides the most direct evidence to date for the interface-enhanced T c in this compound. The observations offer an avenue to higher T c.