Correlation, doping and interband effects on the optical conductivity of iron superconductors

TL;DR

This paper investigates how electronic interactions, doping, and interband effects influence the optical conductivity in iron superconductors, revealing that interband transitions dominate the spectral weight and challenge single-band assumptions.

Contribution

It demonstrates that in multiorbital iron superconductors, interband transitions significantly affect optical spectra, unlike in single-band systems where kinetic energy renormalization suffices.

Findings

Interband transitions are strongly enhanced by interactions.

The Drude weight suppression is dominated by interband effects.

Single-band kinetic energy renormalization does not apply to multiorbital systems.

Abstract

Electronic interactions in multiorbital systems lead to non-trivial features in the optical spectrum. In iron superconductors the Drude weight is strongly suppressed with hole-doping. We discuss why the common association of the renormalization of the Drude weight with that of the kinetic energy, used in single band systems, does not hold in multi-orbital systems. This applies even in a Fermi liquid description when each orbital is renormalized differently, as it happens in iron superconductors. We estimate the contribution of interband transitions at low energies. We show that this contribution is strongly enhanced by interactions and dominates the coherent part of the spectral weight in hole-doped samples at frequencies currently used to determine the Drude weight.