Unconventional superconductivity mediated by nematic fluctuations in a multiorbital system: Application to doped FeSe

In unconventional superconductors, pairing is believed to be of electronic origin, and linked to critical collective fluctuations. Here, the authors investigate how nematic fluctuations, responsible for orbital polarization, mediate pairing in doped FeSe. They show that nematic-mediated pairing is highly unconventional and leads to a highly anisotropic gap structure. This in turn gives rise to pronounced non-BCS behavior of observables. The authors compute thermodynamic, spectroscopic, and transport characteristics, find good agreement with the experimental data, and propose further experiments to test their predictions.