arXiv subjects

Andrei Muratov

Publications and source records attributed to Andrei Muratov.

3 recordsLinked to original sources

arXiv2026

Optical Properties of Iron-Selenide Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$ Single Crystals

With infrared Fourier-transform spectroscopy and spectroscopic ellipsometry we investigated the in-plane reflectance of the superconducting Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$ single crystals with a critical temperature $T_c\approx 34.3$ K over a broad frequency range at temperatures of 4--300 K. The normal-state response of Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$ is analyzed by 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 component in the normal state are presented. We report a Fano-shaped mode at 1430~cm$^{-1}$ indicating a coupling of the discrete mode presumably related to some electronic transition to a two-magnon continuum as well as a low-frequency broad band assigned to the acoustic magnon branch of the antiferromagnetic superstructure. These features persist in the reflectance in both the normal and superconducting states suggesting a mesoscopic coexistence of superconductivity and magnetism in Na$_{0.27}$K$_{0.27}$Rb$_{0.27}$Fe$_{1.7}$Se$_2$.

cond-mat.supr-con↗

arXiv2025

Optical Properties of Superconducting K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ Single Crystals

The optical properties of the superconducting K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ single crystals with a critical temperature $T_c\approx 26$ 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 K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ 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 $\varepsilon _1(ω)$ at $T < T_c$ also evidences the formation of the superconducting condensate. The superconducting plasma frequency $ω_{pl,s} = (213\pm 5)$~cm$^{-1}$ and the magnetic penetration depth $λ=(7.5\pm 0.2)$~$μ$m at $T=5$~K are determined.

cond-mat.supr-con↗

arXiv2023

Morphology and Optical Properties of Thin Cd3As2 Films of a Dirac Semimetal Compound

Using atomic-force microscopy (AFM) and wide-band (0.02-8.5 eV) spectroscopic ellipsometry techniques we investigated morphology and optical properties of Cd3As2 films grown by non-reactive rf magnetron sputtering on two types of oriented crystalline substrates (100)p-Si and (001) alpha-Al2O3. The AFM study revealed grainy morphology of the films due to island incorporation during the film growth. The complex dielectric function spectra of the annealed Cd3As2/Al2O3 films manifest pronounced interband optical transitions at 1.2 and 3.0 eV, in excellent agreement with the theoretical calculations for the body centered tetragonal Cd3As2 crystal structure. We discovered that due to electronic excitations to the Cd(s) conical bands the low-energy absorption edge of the annealed Cd3As2 films reveals linear dependence. We found that for the annealed Cd3As2 films the Cd(s) conical node may be shifted in energy by about 0.08-0.18 eV above the heavy-flat As(p) valence band, determining the optical gap value. The as-grown Cd3As2 films exhibit the pronounced changes of the electronic band structure due to doping effect associated with Cd non-stoichiometry, where fine-tuning of Cd concentration may result in the gapless electronic band structure of Dirac semimetals.

cond-mat.mtrl-sci↗