2025/11/14 by Muratov, Andrei, Rakhmanov, Yevgeny, Shilov, Andrei +2
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.2511.11123
The optical properties of the superconducting K0.8Fe1.7(Se0.73S0.27)2 single crystals with a critical temperature Tc≈ 26 K have been measured in the \it ab plane in a wide frequency range using both infrared Fourier-transform spectroscopy and spectroscopic ellipsometry at temperatures of 4--300 K. The normal-state reflectance of K0.8Fe1.7(Se0.73S0.27)2 is analyzed using a Drude-Lorentz model with one Drude component. The temperature dependences of the plasma frequency, optical conductivity, scattering rate, and dc resistivity of the Drude contribution in the normal state are presented. In the superconducting state, we observe a signature of the superconducting gap opening at 2Δ(5~K) = 11.8~meV. An abrupt decrease in the low-frequency dielectric permittivity ε 1(ω) at T < Tc also evidences the formation of the superconducting condensate. The superconducting plasma frequency ωpl,s = (213± 5)~cm-1 and the magnetic penetration depth λ=(7.5± 0.2)~μm at T=5~K are determined.