Phase diagram and calorimetric properties of NaFe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mi>x</mml:mi></mml:msub></mml:math>As

Wang, A. F.; Luo, X. G.; Yan, Y. J.; Ying, Jianjun; Xiang, Ziji; Ye, G. J.; Cheng, Peng; Li, Z. Y.; Hu, Weijin; Chen, X. H.

doi:10.1103/physrevb.85.224521

Cited by 78 publications

(82 citation statements)

References 47 publications

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“…The parent compound (x ¼ 0) has a SDW phase transition at T SDW ¼ 40 K, and the optimally doped sample (x ¼ 0.028) has a bulk SC transition at T C ¼ 20 K. The underdoped sample that lies in the middle (x ¼ 0.014) is the most interesting one, which shows a structural transition at T S ¼ 32 K, a SDW transition at T SDW ¼ 22 K and a SC transition at T C ¼ 16 K. The three successive transitions are clearly manifested in the specific heat data shown in Fig. 1b and the resistivity results reported previously 17 . The main goal of our STM studies here is to determine whether the SDW-SC coexistence is microscopic or not.…”

Section: Resultssupporting

confidence: 63%

“…The existence of the SC gap at every location of the sample demonstrates that superconductivity is a homogeneous rather than a filamentary phenomenon in this underdoped sample. The direct observation of both the SDW and SC gaps at the same atomic location, plus the fact that the sample exhibits both long-range SDW order and 100% SC volume fraction 17 Competition between the SDW and SC phases. Now the microscopic coexistence of the SDW and SC orders is unambiguously demonstrated, the next question is the interplay between them.…”

Section: Resultsmentioning

confidence: 96%

“…Figure 1a displays the phase diagram of the NaFe 1 À x Co x As system in the underdoped regime around the SDW and SC phase boundary 17 . The solid symbols in the phase diagram represent the SDW and SC transition temperatures of the three samples studied here.…”

Section: Resultsmentioning

confidence: 99%

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Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1−xCoxAs

et al. 2013

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Although the origin of high temperature superconductivity in the iron pnictides is still under debate, it is widely believed that magnetic interactions or fluctuations have a crucial role in triggering Cooper pairing. A key issue regarding the iron pnictide phase diagram is whether long-range magnetic order can coexist with superconductivity microscopically. Here we use scanning tunnelling microscopy to investigate the local electronic structure of underdoped NaFe 1 À x Co x As near the spin density wave and superconducting phase boundary. Spatially resolved spectroscopy directly reveals both the spin density wave and superconducting gaps at the same atomic location, providing compelling evidence for the microscopic coexistence of the two phases. The strengths of the two orders are shown to anti-correlate with each other, indicating the competition between them. This work implies that Cooper pairing in the iron pnictides can occur when portions of the Fermi surface are already gapped by the spin density wave order.

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Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 96%

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Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1−xCoxAs

et al. 2013

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“…The mixtures are put into Al 2 O 3 crucibles, then sealed in iron crucibles under 1.5 atm of high-purity Ar gas. Then the crucible is heated for single-crystal growth [32].…”

Section: Fe-based Superconductorsmentioning

confidence: 99%

Crystal Growth Techniques for Layered Superconductors

Nagao

2017

Condensed Matter

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Layered superconductors are attractive because some of them show high critical temperatures. While their crystal structures are similar, these compounds are composed of many elements. Compounds with many elements tend to be incongruent melting compounds, thus, their single crystals cannot be grown via the melt-solidification process. Hence, these single crystals have to be grown below the decomposition temperature, and then the flux method, a very powerful tool for the growth of these single crystals with incongruent melting compounds, is used. This review shows the flux method for single-crystal growth technique by self-flux, chloride-based flux, and HPHT (high-pressure and high-temperature) flux method for many-layered superconductors: high-T c cuprate, Fe-based and BiS 2 -based compounds.

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“…The mixtures are put into Al2O3 crucibles, then sealed in iron crucibles under 1.5 atm of high-purity Ar gas. Then the crucible is heated for single-crystal growth [32]. There are reports about the growth of Sr4V2O6Fe2As2 single crystals, which is a FeAs self-flux method.…”

Section: Fe-based Superconductorsmentioning

confidence: 99%

Crystal Growth Techniques for Layered Superconductors

Nagao¹

2017

Preprint

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Layered superconductors are attractive because some of them show high critical temperatures. While their crystal structures are similar, those compounds are composed of many elements. Compounds with many elements tend to be incongruent melting compounds, thus, their single crystals cannot be grown via the melt-solidification process. Hence, these single crystals have to be grown below the decomposition temperature, and then the flux method, a very powerful tool for the growth of these single crystals with incongruent melting compounds, is used. This review shows the flux method for single-crystal growth technique by self-flux, chloride-based flux, and HPHT (high-pressure and high-temperature) flux method for many-layered superconductors: high-Tc cuprate, Fe-based and BiS2-based compounds.Keywords: single crystal growth; incongruent melting compound; flux method Crystal Growth of Layered SuperconductorsThis review presents the single-crystal growth of high-Tc cuprate, Fe-based and BiS2-based superconductors as typical layered superconductors. Those layered superconductors form many analogous compounds and show other interesting properties. Additionally, layered superconductors have high anisotropy. In order to reveal such intrinsic properties, their single crystals are necessary. However, layered superconductors are composed of multiple elements and they are incongruent melting compounds. This suggests that the growth of single crystals cannot use the melt-solidification process and, thus, the solution-growth process is necessary. During the single-crystal growth process, the temperature must be lower than the decomposition temperature of the layered superconductors. Hence, the flux method is useful for single-crystal growth of layered superconductors. In this review, the single-crystal growth technique for high-Tc cuprate, Fe-based and BiS2-based compounds using various fluxes are introduced. Single-Crystal Growth Techniques for Incongruent Melting CompoundsIn order to grow single crystals, their raw materials of layered superconductors have to become solution (liquid phase) below the decomposition temperatures of the products. The solvent of that solution (liquid phase) is called "flux". Flux plays a role as a solvent in the solution-growth process. Therefore, flux should be composed of low-melting compounds, such as metals, alkali chlorides, and other compounds with a eutectic composition. The conventional flux method, the traveling solvent floating-zone (TSFZ) method, the top-seeded solution growth (TSSG) method, and the high-pressure and high-temperature (HPHT) flux method are briefly explained in this chapter. The conventional flux method does not have to use a special apparatus, but obtained crystals are small. On the other hand, TSFZ and TSSG methods use special apparatuses which are expensive. However, these methods can grow large-sized crystals, and the HPHT flux method is necessary for single-crystal growth under high pressure.

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Phase diagram and calorimetric properties of NaFe1−xCoxAs

Cited by 78 publications

References 47 publications

Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1−xCoxAs

Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1−xCoxAs

Crystal Growth Techniques for Layered Superconductors

Crystal Growth Techniques for Layered Superconductors

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