Superconductivity in compressed iron: Role of spin fluctuations

The recent discovery of superconductivity in hexagonal iron under pressure poses a question about whether it is of conventional (phonon) or unconventional (magnetic) origin. We present first-principles calculations of the electron-phonon coupling in iron at Pgreater than or similar to15 GPa, and argue that a conventional mechanism can explain the appearance of superconductivity, but not its rapid disappearance at Pgreater than or similar to30 GPa. We suggest that spin fluctuations, ferro- and/or antiferromagnetic, play a crucial role in superconductivity in this case.