Optical conductivity of superconducting K0.8Fe2− ySe2 single crystals: Evidence for a Josephson-coupled phase
نویسندگان
چکیده
The optical properties of the iron-chalcogenide superconductor K0.8Fe2−ySe2 with a critical temperature Tc = 31 K have been measured over a wide frequency range in the ab planes above and below Tc. The conductivity is incoherent at room temperature but becomes coherent (Drude-like) at T Tc; however, R 320 k , well above the threshold for the superconductor-insulator transition atR = h/4e2 6.9 k . Below Tc, the superfluid density ρs0 48 × 103 cm−2 places this material on the scaling line ρs0/8 4.4 σdc Tc, but in a region associated with Josephson coupling, suggesting this material is inhomogeneous and constitutes a Josephson phase.
منابع مشابه
Floating-zone growth of KxFe2-ySe2 single crystals
The discovery of superconductivity at temperatures above 30 K in KxFe2-ySe2 compounds has attracted considerable attention [1]. The crystal structure of KxFe2-ySe2 descends from the well-known ThCr2Si2 structure with vacancies at the Fe sites. It was soon found that magnetism and superconductivity coexist in AxFe2-ySe2 (A = K, Rb, and Cs) [2-3]. Even in single crystals which show full shielding...
متن کاملInfluence of microstructure on superconductivity in KxFe2−ySe2 and evidence for a new parent phase K2Fe7Se8
The search for new superconducting materials has been spurred on by the discovery of iron-based superconductors whose structure and composition is qualitatively different from the cuprates. The study of one such material, KxFe2-ySe2 with a critical temperature of 32 K, is made more difficult by the fact that it separates into two phases-a dominant antiferromagnetic insulating phase K2Fe4Se5, an...
متن کاملEffective medium approximation and the complex optical properties of the inhomogeneous superconductor K0.8Fe2− ySe2
The in-plane optical properties of the inhomogeneous iron-chalcogenide superconductor K0.8Fe2−ySe2 with a critical temperature Tc = 31 K have been modeled in the normal state using the Bruggeman effective medium approximation for metallic inclusions in an insulating matrix. The volume fraction for the inclusions is estimated to be 10%; however, they appear to be highly distorted, suggesting a f...
متن کاملEvolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals
We study the relationship between precipitate morphology and superconductivity in KxFe1.6+ySe2 single crystals grown by self-flux method. Scanning electron microscopy (SEM) measurements revealed that the superconducting phase forms a network in the samples quenched above iron vacancy order-disorder transition temperature Ts, whereas it aggregates into micrometer-sized rectangular bars and align...
متن کاملTransverse Optical Plasmons in Layered Superconductors.
We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel. We consider both bilayer superlattices, and single layer lattices with a spread of interlayer Jo...
متن کامل