Inhomogeneous superconductivity induced by interstitial Fe deintercalation in oxidizing-agent-annealed and HNO3-treated Fe1+y(Te1-xSex)

Abstract

We have systematically investigated the annealing effect on the superconductivity of iron chalcogenide Fe1+y(Te1-xSex). The atmospheres used for annealing include O2, N2, I2 vapor, air and vacuum. We observed that annealing in O2, I2 and air could enhance superconductivity for the underdoped samples, consistent with the results reported in literatures. Interestingly, we found that annealing in N2 also leads to superconductivity enhancement, similar to the annealing effects of O2, I2 and air. However, vacuum annealing does not enhance superconductivity, which indicates that the enhanced superconductivity in O2-, N2-, I2- and air-annealed samples is not due to improved homogeneity. In addition, we have treated the underdoped samples with nitric acid, which is found to enhance superconductivity as well. Our analyses of these results support the argument that the superconductivity enhancement, caused either by annealing or nitric acid treatment, originates from the variation of interstitial Fe. The interstitial Fe, which is destructive to superconducting pairing, can be reduced by annealing in oxidation agents or nitric acid treatment. We also find that although N2-, O2- and air-annealed samples exhibit strong superconducting diamagnetism with -4pichi ~1 (chi, dc magnetic susceptibility) for some samples, their actual superconducting volume fraction probed by specific heat is low, ranging from 10% to 30% for 0.09 < x < 0.3, indicating that the superconductivity suppression remains significant even in annealed samples. The strong diamagnetism is associated with the superconducting shielding effect on the non-superconducting phase. We have also established the phase diagram of the annealed samples and compared it with that of the as-grown samples. The effect of annealing on the interplay between magnetism and superconductivity is discussed.

References in corpus (26)

• Structural and magnetic phase diagram of CeFeAsO1-xFx and its relationship to high-temperature superconductivity
• Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe)
• Incommensurate magnetic order in the alpha-Fe(Te,Se) superconductor systems
• Very High Field Two-Band Superconductivity in LaFeAsO_0.89F_0.11
• Nearly Isotropic superconductivity in (Ba,K)Fe2As2
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Bulk Superconductivity at 14 K in Single Crystals of Fe1+yTexSe1-x
• The electronic phase diagram of the LaO1-xFxFeAs superconductor
• Anomalous suppression of the orthorhombic distortion in superconducting Ba[Fe(1-x)Cox]2As2
• Coexistence of the spin-density-wave and superconductivity in the (Ba,K)Fe2As2
• Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal
• Coexistence of static magnetism and superconductivity in SmFeAsO1-xFx as revealed by muon spin rotation
• From (pi, 0) magnetic order to superconductivity with (pi, pi) magnetic resonance in Fe1.02(Te1-xSex)
• Charge carrier localization induced by excess Fe in the Fe1+y(Te,Se) superconductor system
• Determination of anisotropic Hc2 up to 60 T in (Ba0.55K0.45)Fe2As2 single crystals
• Weak anisotropy of the superconducting upper critical field in Fe1.11Te0.6Se0.4 single crystals
• Pauli-limited upper critical field in Fe1+yTe1-xSex
• Evidence for dominant Pauli paramagnetic effect in the upper critical fields of a FeTe0.6Se0.4 superconductor
• Psuedo-isotropic upper critical field in cobalt-doped SrFe2As2 epitaxial films
• Revised Phase Diagram for FeTe1-xSex system with less excess Fe atoms
• Upper critical fields of the 11-system iron-chalcogenide superconductor FeSe${}_{0.25}$Te${}_{0.75}$
• Evolution of superconductivity by oxygen annealing in FeTe0.8S0.2
• Interstitial Iron Controlled Superconductivity in Fe1+xTe0.7Se0.3
• Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal
• Superconductivity in oxygen-annealed FeTe1-xSx single crystal
• Specific-heat study of superconducting and normal states in FeSe1-xTex (0.6<=x<=1) single crystals: Strong-coupling superconductivity, strong electron-correlation, and inhomogeneity

Cited by in corpus (9)

• Large, Homogeneous, and Isotropic Critical Current Density in Oxygen-Annealed Fe1+yTe0.6Se0.4 Single Crystal
• Coupling of electronic and magnetic properties in Fe1+y(Te1-xSex)
• Bulk Superconductivity in Fe1+yTe0.6Se0.4 Induced by Removal of Excess Fe
• Superconducting Symmetry Studied from Impurity Effects in Single-Crystal Fe1-yMySe0.3Te0.7 (M = Co, Ni, Zn)
• On the role of chalcogen vapor annealing in inducing bulk superconductivity in Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$
• Nano-scale Inhomogeneous Superconductivity in Fe(Te1-xSex) Probed by Nanostructure-transport
• Molecular beam epitaxy preparation and in situ characterization of FeTe thin films
• Possible nodal superconducting gap in Fe${}_{1+y}$(Te${}_{1-x}$Se${}_x$) single crystals from ultra-low temperature penetration depth measurements
• Interfacially enhanced superconductivity in Fe(Te,Se)/Bi4Te3 heterostructures