Electron-boson spectral density of LiFeAs obtained from optical data

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• LiFeAs is a superconductor with potential for technological applications.
• Understanding the electron-boson interaction is crucial for explaining superconductivity mechanisms.

Purpose of the Study:

• To determine the electron-boson spectral density of LiFeAs using optical data.
• To investigate the nature of the observed spectral features and their persistence.

Main Methods:

• Analysis of existing optical data in the superconducting state of LiFeAs at 4 K.
• Application of a maximum entropy technique to extract the spectral density I(2)χ(ω) from the optical scattering rate.
• Consideration of elastic impurity scattering effects.

Main Results:

• A robust peak in the electron-boson spectral density I(2)χ(ω) was identified, centered around 8.0 meV (5.3 k(B)Tc).
• This spectral feature aligns with findings from scanning tunneling spectroscopy (STS) and inelastic neutron scattering (INS).
• The peak was observed to persist even in the normal state of LiFeAs at 23 K.

Conclusions:

• The study successfully recovered the electron-boson spectral density of LiFeAs, revealing a significant interaction feature.
• The observed peak's persistence in the normal state suggests its origin is not solely tied to the superconducting condensate.
• Evidence for an anisotropic superconducting gap in LiFeAs was found, consistent with angular resolved photoemission (ARPES) data.