Probing structural, magnetic, and superconducting properties of iron-based superconductors by dynamical mean field theory and quantum Monte Carlo methods

by MIchele Casula (CNRS and Institut de Min eralogie, de Physique des Materiaux et de Cosmochimie, Universite Pierre et Marie Curie)

Wednesday 15 Feb 2017, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dipartimento di Fisica - Ed. G. Marconi)

In this talk I will illustrate how dynamical mean eld theory (DMFT) and quantum Monte Carlo (QMC) simulations can shed light on the complex physics behind iron-based superconductors. The normal state of BaFe2As2 is investigated by DMFT, including a dynamically screened Hubbard interaction, derived from first principles. The DMFT spectral function is strongly doping- and temperature-dependent, showing a Fermi liquid to bad metal crossover in the overdoped region. Charge density waves and superconductivity are studied by QMC in FeSe under pressure. Spin  fluctuations have a strong collinear character, while the resulting superconducting order parameter includes planar s-wave and d-wave symmetry channels, both preserving the full A1g representation. These results can rationalize a series of contradictory experimental findings, such as the observation of twofold symmetry in the FeSe bulk superconducting phase, and nodeless gap in FeSe monolayer.