Non-Fermi-liquid scattering rates and anomalous band dispersion in ferropnictides

TL;DR

This study uses ARPES to investigate non-Fermi-liquid behavior in ferropnictides, revealing linear energy-dependent scattering rates and their impact on band dispersion and superconductivity, indicating a BCS-BEC crossover.

Contribution

It provides new insights into the orbital-dependent scattering rates and their role in anomalous band dispersion in ferropnictides.

Findings

Linear-in-energy scattering rates observed

Weakly dispersing bands with strong mass enhancement

Small effective Fermi energy suggests BCS-BEC crossover

Abstract

Angle-resolved photoemission spectroscopy (ARPES) is used to study the band dispersion and the quasiparticle scattering rates in two ferropnictides systems. Our ARPES results show linear-in-energy dependent scattering rates which are constant in a wide range of control parameter and which depend on the orbital character of the bands. We demonstrate that the linear energy dependence gives rise to weakly dispersing band with a strong mass enhancement when the band maximum crosses the chemical potential. In the superconducting phase the related small effective Fermi energy favors a Bardeen-Cooper-Schrieffer (BCS)\,\cite{Bardeen1957}-Bose-Einstein (BE)\,\cite{Bose1924} crossover state.