Hidden T-linear scattering rate in Ba0.6K0.4Fe2As2 revealed by optical spectroscopy

Area of Science:

• Condensed matter physics
• Materials science
• Solid-state physics

Background:

• Barium potassium iron arsenide (Ba0.6K0.4Fe2As2) is a pnictide superconductor.
• Understanding the normal state electronic properties is crucial for elucidating superconductivity mechanisms.

Purpose of the Study:

• To investigate the optical conductivity of Ba0.6K0.4Fe2As2 in its normal state.
• To identify the charge carrier dynamics and scattering mechanisms.

Main Methods:

• Optical conductivity measurements were performed over a wide frequency range and at various temperatures.
• The real part of the optical conductivity, σ1(ω), was analyzed using a two-Drude model.

Main Results:

• Two distinct Drude components, characterized by different scattering rates (1/τ), were identified.
• A temperature-independent scattering rate (1/τb) for a broad component and a temperature-linear scattering rate (1/τn) for a narrow component were observed.
• The temperature-linear scattering rate and resistivity (ρn) suggest scattering from spin fluctuations.

Conclusions:

• The observed temperature-linear scattering in Ba0.6K0.4Fe2As2 is attributed to spin fluctuations.
• This finding indicates the likely presence of an antiferromagnetic quantum critical point within the superconducting dome of this material.