Infrared Measurement of the Pseudogap in P-Doped and Co-Doped BaFe2As2 High-Temperature Superconductors

TL;DR

This study uses infrared spectroscopy to investigate the pseudogap phenomenon in BaFe2As2-based high-temperature superconductors, revealing its relation to magnetic fluctuations and distinguishing it from the superconducting gap.

Contribution

It provides the first infrared evidence of a pseudogap in BaFe2As2 superconductors and clarifies its independence from superconductivity and connection to magnetic fluctuations.

Findings

Infrared pseudogap magnitude matches the spin-density-wave gap.

Pseudogap is unrelated to superconducting gap.

Pseudogap correlates with antiferromagnetic fluctuations.

Abstract

We report on infrared studies of charge dynamics in a prototypical pnictide system: the BaFe2As2 family. Our experiments have identified hallmarks of the pseudogap state in the BaFe2As2 system that mirror the spectroscopic manifestations of the pseudogap in the cuprates. The magnitude of the infrared pseudogap is in accord with that of the spin-density-wave gap of the parent compound. By monitoring the superconducting gap of both P- and Co-doped compounds, we find that the infrared pseudogap is unrelated to superconductivity. The appearance of the pseudogap is found to correlate with the evolution of the antiferromagnetic fluctuations associated with the spin-density-wave instability. The strong-coupling analysis of infrared data further reveals the interdependence between the magnetism and the pseudogap in the iron pnictides.