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Mitchell, Jonathan E.; Saparov, Bayrammurad; Lin, Wenzhi; Calder, Stuart; Li, Qing; Kalinin, Sergei V.; Pan, Minghu; Christianson, A. D.; Sefat, Athena S.

doi:10.1103/physrevb.86.174511

Cited by 9 publications

(10 citation statements)

References 38 publications

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“…Gap inhomogeneity exists in most doped superconductors, including Fe-based materials, however, the majority of the materials are bulk superconductors, showing only nanoscale variation of the gap (see Refs. 15,[33][34][35][36][37][38]. The appearance of a non-superconductive phase and related phase separation explains the filamentary nature of the superconductivity in this material and is in agreement with the bulk measurements.…”

supporting

confidence: 73%

“…However, such a gap structure varies spatially; the STS curves mea- sured on the clover-like defect (see upper star in Fig.4b) show a gap size as large as 30 meV with no prominent coherence peaks (red curve in Fig.4c). To further investigate the gap distribution we took a differential tunneling conductance spectra (dI/dV versus V ) survey on a large surface area, using the previously explored method [31][32][33] (see Fig.4d). Fig.4e shows three representative tunneling spectra for superconducting (red and green curves) and normal state (blue curve) regions.…”

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confidence: 99%

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Local Inhomogeneity and Filamentary Superconductivity in Pr-DopedCaFe2As2

et al. 2014

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We use multi-scale techniques to determine the extent of local inhomogeneity and superconductivity in Ca0.86Pr0.14Fe2As2 single crystal. The inhomogeneity is manifested as a spatial variation of praseodymium concentration, local density of states, and superconducting order parameter. We show that the high-Tc superconductivity emerges from clover-like defects associated with Pr dopants. The highest Tc is observed in both the tetragonal and collapsed tetragonal phases, and its filamentary nature is a consequence of non-uniform Pr distribution that develops localized, isolated superconducting regions within the crystals.

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confidence: 73%

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confidence: 99%

Local Inhomogeneity and Filamentary Superconductivity in Pr-DopedCaFe2As2

et al. 2014

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“…Although the surfaces of BaFe 2 As 2 are known to reconstruct, the superconducting gaps from different surface reconstruction are expected to be almost identical since the superconductivity is a global property and ~3 nm coherence lengths are found for these materials 53–55 . In fact, for Ba 0.5 Sr 0.5 (Fe 1−x Co x ) 2 As 2 with x = 0.073 as-grown crystal ( T c = 17 K), scanning tunneling microscopy/spectroscopy (STM/S) results of at 4.3 K found inhomogeneous gap values from about 3 meV down to 0 meV 20 . For Ba(Fe 1−x Co x ) 2 As 2 crystals, Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Moreoever, the magnetic susceptibility of Ba(Fe 1−x Co x ) 2 As 2 crystals with 0.04 ≤ x ≤ 0.14 showed an increase of T c values by ~1 to 3 K, with no significant change in superconducting Meissner or shielding fractions 19 . In addition, annealing (800 °C, 1 week) of Ba 0.5 Sr 0.5 (Fe 1−x Co x ) 2 As 2 with x = 0.14 showed a T c increase of 5 K in bulk properties, and a decrease in heat capacity γ o of more than half 20 . In all of these examples, it is assumed that annealed crystals have improved crystallinity due to the release of residual strain, hence improve T N or T c .…”

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confidence: 97%

Improving superconductivity in BaFe2As2-based crystals by cobalt clustering and electronic uniformity

Zheng

Zou

et al. 2017

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Quantum materials such as antiferromagnets or superconductors are complex in that chemical, electronic, and spin phenomena at atomic scales can manifest in their collective properties. Although there are some clues for designing such materials, they remain mainly unpredictable. In this work, we find that enhancement of transition temperatures in BaFe2As2-based crystals are caused by removing local-lattice strain and electronic-structure disorder by thermal annealing. While annealing improves Néel-ordering temperature in BaFe2As2 crystal (T N = 132 K to 136 K) by improving in-plane electronic defects and reducing overall a-lattice parameter, it increases superconducting-ordering temperature in optimally cobalt-doped BaFe2As2 crystal (T c = 23 to 25 K) by precipitating-out the cobalt dopants and giving larger overall a-lattice parameter. While annealing improves local chemical and electronic uniformity resulting in higher T N in the parent, it promotes nanoscale phase separation in the superconductor resulting in lower disparity and strong superconducting band gaps in the dominant crystal regions, which lead to both higher overall T c and critical-current-density, J c.

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“…3a. The gap map was obtained by performing the gap-fitting procedure similar to the method reported in reference [21], as outlined in references [17,22]. The gap map clearly visualizes that superconductivity is suppressed at sites of Fe/Te aggregation.…”

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Role of chalcogen vapor annealing in inducing bulk superconductivity inFe1+yTe1−xSex

et al. 2015

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Recent investigations have shown that Fe1+yTe1−xSex can be made superconducting by annealing it in Se and O vapors. The current lore is that these chalcogen vapors induce superconductivity by removing the magnetic excess Fe atoms. To investigate this phenomenon we performed a combination of magnetic susceptibility, specific heat and transport measurements together with scanning tunneling microscopy and spectroscopy and density functional theory calculations on Fe1+yTe1−xSex treated with Te vapor. We conclude that the main role of the Te vapor is to quench the magnetic moments of the excess Fe atoms by forming FeTem (m ≥ 1) complexes. We show that the remaining FeTem complexes are still damaging to the superconductivity and therefore that their removal potentially could further improve superconductive properties in these compounds.

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Temperature-composition phase diagrams for Ba1−xSrxFe2

Cited by 9 publications

References 38 publications

Local Inhomogeneity and Filamentary Superconductivity in Pr-DopedCaFe2As2

Local Inhomogeneity and Filamentary Superconductivity in Pr-DopedCaFe2As2

Improving superconductivity in BaFe2As2-based crystals by cobalt clustering and electronic uniformity

Role of chalcogen vapor annealing in inducing bulk superconductivity inFe1+yTe1−xSex

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