Electron-boson spectral density of LiFeAs obtained from optical data

J. Hwang; J. P. Carbotte; B. H. Min; Y. S. Kwon; T. Timusk

doi:10.1088/0953-8984/27/5/055701

paper

Electron-boson spectral density of LiFeAs obtained from optical data

arXiv:1412.5818 · doi:10.1088/0953-8984/27/5/055701

Abstract

We analyze existing optical data in the superconducting state of LiFeAs at $T =$ 4 K, to recover its electron-boson spectral density. A maximum entropy technique is employed to extract the spectral density $I^{2} χ (ω)$ from the optical scattering rate. Care is taken to properly account for elastic impurity scattering which can importantly affect the optics in an $s$ -wave superconductor, but does not eliminate the boson structure. We find a robust peak in $I^{2} χ (ω)$ centered about $Ω_{R} ≅$ 8.0 meV or 5.3 $k_{B} T_{c}$ (with $T_{c} =$ 17.6 K). Its position in energy agrees well with a similar structure seen in scanning tunneling spectroscopy (STS). There is also a peak in the inelastic neutron scattering (INS) data at this same energy. This peak is found to persist in the normal state at $T =$ 23 K. There is evidence that the superconducting gap is anisotropic as was also found in low temperature angular resolved photoemission (ARPES) data.

17 pages, 6 figures

Electron-boson spectral density of LiFeAs obtained from optical data

Abstract

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