Unusual Pseudogap-like Features Observed in Iron Oxypnictide Superconductors

TL;DR

This study investigates pseudogap-like features in iron oxypnictide superconductors LaFeAsO:F and LaFePO:F using laser photoemission, revealing temperature-dependent pseudogaps in high-Tc samples and comparing them to cuprates.

Contribution

It reports the observation of pseudogap-like features in iron oxypnictides and discusses their possible origins, highlighting differences between high-Tc and low-Tc compounds.

Findings

High-Tc LaFeAsO:F shows a temperature-dependent pseudogap at 250 K.

Low-Tc LaFePO:F lacks the pseudogap feature.

Both compounds exhibit ~20 meV pseudogaps and superconducting gap signatures.

Abstract

We have performed a temperature-dependent angle-integrated laser photoemission study of iron oxypnictide superconductors LaFeAsO:F and LaFePO:F exhibiting critical transition temperatures (Tc's) of 26 K and 5 K, respectively. We find that high-Tc LaFeAsO:F exhibits a temperature-dependent pseudogap-like feature extending over ~0.1 eV about the Fermi level at 250 K, whereas such a feature is absent in low-Tc LaFePO:F. We also find ~20-meV pseudogap-like features and signatures of superconducting gaps both in LaFeAsO:F and LaFePO:F. We discuss the possible origins of the unusual pseudogap-like features through comparison with the high-Tc cuprates.