Direct Observation of Microstructures on Superconducting Single Crystals of K${}_x$Fe${}_{2-y}$Se${}_2$

Abstract

Potassium intercalated FeSe has been reported as a superconductor with superconducting transition temperatures ($T_{\mathrm{c}}$'s) of 30-48 K. However, there is no clear answer to identify the relationship between the surface morphology, compositional ratio and its crystal structure. This report directly reveals the correspondence among these three characteristics in single crystals with a $T_{\mathrm{c}}$ onset of around 44 K using a micro-sampling technique. Island-like parts on the surface of the crystals clearly have the K${}_x$Fe${}_2$Se${}_2$ structure with perfect FeSe layers, which is formed in conjunction with the K${}_2$Fe${}_4$Se${}_5$ phase. This results in the appearance of the $T_{\mathrm{c}}$ onset of 44 K.

15 pages, 6 figures

References in corpus (14)

• Fe-based high temperature superconductivity with Tc=31K bordering an insulating antiferromagnet in (Tl,K)FexSe2 Crystals
• Superconductivity at 32 K in single crystal Rb${}_{0.78}$Fe${}_2$Se${}_{1.78}$}
• Superconducting Phases in Potassium-Intercalated Iron Selenides
• Superconductivity at 32K and anisotropy in Tl0.58Rb0.42Fe1.72Se2 crystals
• Transport properties of the new Fe-based superconductor KxFe2Se2 (Tc = 33 K)
• Intrinsic phase separation in superconducting K0.8Fe1.6Se2 (Tc= 31.8 K) single crystals
• Phase relations in K_xFe_{2-y}Se_2 and the structure of superconducting K_xFe_2Se_2 via high-resolution synchrotron diffraction
• Superconductivity and Magnetic Properties of high-quality single crystals of $A_x$Fe${}_2$Se${}_2$ ($A$ = K and Cs)
• Structure, magnetic order and excitations in the 245 family of Fe-based superconductors
• Superconductivity at 44 K in K intercalated FeSe system with excess Fe
• Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals
• Direct observation of nanoscale interface phase in the superconducting chalcogenide K${}_x$Fe${}_{2-y}$Se${}_2$ with intrinsic phase separation
• Spectromicroscopy of electronic phase separation in K${}_x$Fe${}_{2-y}$Se${}_2$ superconductor
• Structure and composition of the superconducting phase in alkali iron selenide K${}_y$Fe${}_{1.6+x}$Se${}_2$

Cited by in corpus (3)

• Intermittent dynamics of antiferromagnetic phase in inhomogeneous iron-based chalcogenide superconductor
• Phase-separation control of K${}_x$Fe${}_{2-y}$Se${}_2$ superconductor through rapid-quenching process
• Quenching Dependence on Superconductivity in the Synthesizing Process of Single Crystals of Rb${}_x$Fe${}_{2-y}$Se${}_2$