The change of electronic state and crystal structure by post-annealing in superconducting SrFe2(As0.65P0.35)2

Abstract

We investigated the annealing effects on the physical properties of SrFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ ($x=0.35$). The superconducting transition temperature ($T_c$) increased from 26 K to 33 K by annealing. The X-ray diffraction measurement suggested that the annealed crystals have the shorter/longer $a/c$-axes and the larger pnictogen height $h_{\mathrm{Pn}}$. This must be linked to the $T_c$-enhancement by annealing. Moreover, it was found that the post-annealing decreased the electronic specific heat coefficient at $T$=0 K, ${\gamma }_r$, and changed the magnetic field ($H$) dependence from sub-linear ${\gamma }_r\propto H^{0.7}$ to $H$-linear ${\gamma }_r\propto H$. This can be attributed the electronic change from dirty to clean superconductors with $s_{\pm }$ gap.

5 pages, 3 figures, accepted for publication in Phys. Rev. B

References in corpus (4)

• Effect of Structural Parameters on Superconductivity in Fluorine-Free LnFeAsO1-y (Ln=La,Nd)
• Effect of annealing on the specific heat of Ba(Fe1-xCox)2As2
• Specific Heat Discontinuity DeltaC vs Tc in Annealed Ba(Fe1-xCox)2As2
• Investigation of the Superconducting Gap Structure in SrFe${}_2$(As${}_{0.7}$P${}_{0.3}$)${}_2$ by Magnetic Penetration Depth and Flux Flow Resistivity Analysis

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• Electronic Phase Diagram of SrFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$: Effect of Structural Dimensionality
• NMR evidence for an intimate relationship between antiferromagnetic spin fluctuations and extended s-wave superconductivity in mono-crystalline SrFe2(As_{1-x}P_{x})2
• Strongly three-dimensional electronic structure and Fermi Surfaces of SrFe${}_2$(As${}_{0.65}$P${}_{0.35}$)${}_2$: Comparison with BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
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• Band-dependent superconducting gap in SrFe${}_2$(As${}_{0.65}$P${}_{0.35}$)${}_2$ studied by angle-resolved photoemission spectroscopy