Direct observation of a Fermi liquid-like normal state in an iron-pnictide superconductor

Alona Tytarenko; Yingkai Huang; Anne de Visser; Steve Johnston; Erik van Heumen

doi:10.1038/srep12421

paper

Direct observation of a Fermi liquid-like normal state in an iron-pnictide superconductor

arXiv:1505.05139 · doi:10.1038/srep12421

Abstract

There are two prerequisites for understanding high-temperature (high-T $_{c}$ ) superconductivity: identifying the pairing interaction and a correct description of the normal state from which superconductivity emerges. The nature of the normal state of iron-pnictide superconductors, and the role played by correlations arising from partially screened interactions, are still under debate. Here we show that the normal state of carefully annealed electron-doped BaFe $_{2 - x}$ Co $_{x}$ As $_{2}$ at low temperatures has all the hallmark properties of a local Fermi liquid, with a more incoherent state emerging at elevated temperatures, an identification made possible using bulk-sensitive optical spectroscopy with high frequency and temperature resolution. The frequency dependent scattering rate extracted from the optical conductivity deviates from the expected scaling $M_{2} (ω, T) \propto (ℏ ω)^{2} + (p π k_{B} T)^{2}$ with $p \approx$ 1.47 rather than $p$ = 2, indicative of the presence of residual elastic resonant scattering. Excellent agreement between the experimental results and theoretical modeling allows us to extract the characteristic Fermi liquid scale $T_{0} \approx$ 1700 K. Our results show that the electron-doped iron-pnictides should be regarded as weakly correlated Fermi liquids with a weak mass enhancement resulting from residual electron-electron scattering from thermally excited quasi-particles.

6+9pages, 3+9 figures To be published in Scientific Reports

Direct observation of a Fermi liquid-like normal state in an iron-pnictide superconductor

Abstract

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