Orbital-selective pairing and superconductivity in iron selenides

Abstract

Unconventional superconductivity: Orbital selective pairing in iron selenides Orbital-selective pairing could explain the unusual properties observed in the unconventional superconductor iron selenide. Conventional superconductivity arises when electrons form Cooper pairs due to electron-phonon coupling. In some materials, however, unconventional superconductivity can arise, which is driven by electron-electron rather than electron-phonon couplings. The detailed mechanism that facilitates electron pairing in unconventional systems remains elusive but iron selenide systems could help to provide insights as they exhibit both relatively high temperature superconductivity, and also strong electron correlations. With different experiments suggesting different pairing mechanisms, however, these systems are somewhat puzzling. An international team of researchers led by Qimiao Si from Rice University now theoretically demonstrate that an orbital-selective pairing state could explain this unusual behaviour, which may also be at play in other unconventional superconductors such as heavy fermion and organic systems.