ﻻ يوجد ملخص باللغة العربية
We systematically studied in-plane optical conductivity of FeSe$_{1-x}$Te$_{x}$ thin films fabricated on CaF$_{2}$ substrates for $x$ = 0, 0.1, 0.2, and 0.4. This system shows a large enhancement of superconducting transition temperature $T_{mathrm{c}}$ at $x sim$ 0.2 and a gentle decrease in $T_{mathrm{c}}$ with further increasing $x$. The low-energy optical conductivity spectrum is described by the sum of narrow and broad Drude components, associated with coherent and incoherent charge dynamics, respectively. With increasing Te content, the spectral weight of the narrow Drude component decreases, while the total weight of the two Drude components increases. As a consequence, the fraction of the narrow Drude weight significantly decreases, indicating that Te substitution leads to stronger electronic correlations. Below the nematic transition temperature, the narrow Drude weight decreases with decreasing temperature. This indicates the reduction of the coherent carrier density, resulting from the Fermi-surface modification induced by the development of the orbital order. The reduction of the narrow Drude weight with temperature stopped at $x sim$ 0.2, corresponding to the disappearance of the nematic transition. Our result suggests that the increase in the coherent carrier density induced by the suppression of the nematic transition gives rise to the enhancement of $T_{mathrm{c}}$. The decrease in $T_{mathrm{c}}$ with further Te substitution likely arises from too strong electronic correlations, which are not favorable for superconductivity.
The spontaneous appearance of nematicity, a state of matter that breaks rotation but not translation symmetry, is one of the most intriguing property of the iron based superconductors (Fe SC), and has relevance for the cuprates as well. Establishing
Using electronic Raman spectroscopy, we report direct measurements of charge nematic fluctuations in the tetragonal phase of strain-free Ba(Fe$_{1-x}$Co$_{x})_{2}$As$_{2}$ single crystals. The strong enhancement of the Raman response at low temperatu
We study the effect of Hunds splitting of repulsive interactions on electronic phase transitions in the multiorbital topological crystalline insulator Pb$_{1-x}$Sn$_{x}$Te, when the chemical potential is tuned to the vicinity of low-lying Type-II Van
Spectroscopic ellipsometry is used to determine the dielectric function of the superconducting LaFeAsO$_{0.9}$F$_{0.1}$ ($T_c$ = 27 K) and undoped LaFeAsO polycrystalline samples in the wide range 0.01-6.5 eV at temperatures 10 $leq T leq$ 350 K. The
We measured the complex conductivity, $sigma$, of FeSe$_{1-x}$Te$_x$ ($x=0-0.5$) films in the superconducting state which show a drastic increase of the superconducting transition temperature, $T_textrm{c}$, when the nematic order disappears. Since t