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The influence of proton irradiation on the fluctuation-induced magnetoconductivity of high quality FeSe _1− _x Te _x ( x = 0.4, 0.55) (FST) thin films has been investigated. The measurements were performed with magnetic fields up to 13 T applied in the two main crystal directions. The results were interpreted in terms of the Ginzburg–Landau approach for three-dimensional materials under a total-energy cutoff. The analysis shows that properly-tuned proton irradiation does not appreciably affect fundamental superconducting parameters like the T _c value, the upper critical fields or the anisotropy. This has important consequences from the point of view of possible applications due to the enhancement of vortex pinning induced by irradiation.

We have measured the reflectivity spectra of the LiFeAs ( T _c = 17.6 K) single crystal in the temperature range from 4 to 300 K. In the superconducting (SC) state ( T T _c ), the optical conductivity spectra display typical metallic behavior with the Drude-type spectra at low frequencies, but we found that the introduction of the two Drude components best fits the data, indicating the multiband nature of this compound. A theoretical analysis of the low-temperature data ( T = 4 K 200 cm ^−1 ), we have also performed the local-density approximation band calculation and calculated the optical spectra of the interband transitions. This theoretical result provided qualitative agreement with the experimental data below 4000 cm ^−1 .

The influence of proton irradiation on the fluctuation-induced magnetoconductivity of high quality FeSe1-xTex (x=0.4, 0.55) (FST) thin films has been investigated. The measurements were performed with magnetic fields up to 13 T applied in the two main crystal directions. The results were interpreted in terms of the Ginzburg-Landau approach for three-dimensional materials under a total-energy cutoff. The analysis shows that properly-tuned proton irradiation does not appreciably affect fundamental superconducting parameters like the Tc value, the upper critical fields or the anisotropy. This has important consequences from the point of view of possible applications due to the enhancement of vortex pinning induced by irradiation. [ABSTRACT FROM AUTHOR]

We report the observation of pseudogap (PG) behavior in optical conductivity in an underdoped Ba0.6+δK0.4-δFe2As2 (T onset c ≈ 36 K) single crystal far above Tc, up to 100K (≈ 3Tc). Wide separation of the energy scales of the magnetic and superconducting (SC) correlations in the Ba0.6+δK0.4-δFe2As2 sample enabled us to establish that the PG structures observed in optical conductivity in the range of 50-150 cm-1 are uniquely driven by the SC correlation, and the magnetic correlation coexists in the far separated range of about 700 cm-1. Theoretical calculations, based on the preformed Cooper pair model, provided an excellent description of the temperature evolution of the SC correlation in optical conductivity data from below to above Tc. [ABSTRACT FROM AUTHOR]