Electronic structure of optimally doped pnictide Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$: a comprehensive ARPES investigation

TL;DR

This comprehensive ARPES study reveals the detailed electronic structure of the optimally doped Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ superconductor, highlighting Fermi surface topology, band renormalization, and correlation effects.

Contribution

The paper provides a detailed experimental mapping of the electronic structure and Fermi surfaces, with band fitting parameters for theoretical modeling of this Fe-based superconductor.

Findings

Four dispersive bands crossing the Fermi level

Nested Fermi surface pockets connected by antiferromagnetic wavevector

Bandwidth reduced by factor of 2, mass renormalization by factor of 4

Abstract

We have conducted a comprehensive angle-resolved photoemission study on the normal state electronic structure of the Fe-based superconductor Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$. We have identified four dispersive bands which cross the Fermi level and form two hole-like Fermi surfaces around $\Gamma$ and two electron-like Fermi surfaces around M. There are two nearly nested Fermi surface pockets connected by an antiferromagnetic ($\pi$, $\pi$) wavevector. The observed Fermi surfaces show small $k_z$ dispersion and a total volume consistent with Luttinger theorem. Compared to band structure calculations, the overall bandwidth is reduced by a factor of 2. However, many low energy dispersions display stronger mass renormalization by a factor of $\sim$ 4, indicating possible orbital (energy) dependent correlation effects. Using an effective tight banding model, we fitted the band structure and the Fermi surfaces to obtain band parameters reliable for theoretical modeling and calculations of the important physical quantities, such as the specific heat coefficient.