Superconductivity in CeOBiS2 with cerium valence fluctuation

Nagao, Masanori; Miura, Akira; Ueta, Ikuo; Watauchi, Satoshi; Tanaka, Isao

doi:10.1016/j.ssc.2016.07.017

Cited by 32 publications

(43 citation statements)

References 25 publications

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“…Such a situation is known to occur in so-called “self-doped” EuFBiS 2 superconductor 14 in which Eu appears in mixed valence state with coexistence of Eu 2+ and Eu 3+ . Very recent observation of superconductivity in stoichiometric CeOBiS 2 system 15 may therefore apparently support the analogy with the self-doped systems. However, the interplay between the rare-earth mixed valence and the rare-earth-to-Bi charge-transfer is not that simple.…”

Section: Introductionmentioning

confidence: 76%

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Metallic phase in stoichiometric CeOBiS2 revealed by space-resolved ARPES

Sugimoto

Paris

Wakita

et al. 2018

Sci Rep

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Recently CeOBiS2 system without any fluorine doping is found to show superconductivity posing question on its origin. Using space resolved ARPES we have found a metallic phase embedded in the morphological defects and at the sample edges of stoichiometric CeOBiS2. While bulk of the sample is semiconducting, the embedded metallic phase is characterized by the usual electron pocket at X point, similar to the Fermi surface of doped BiS2-based superconductors. Typical size of the observed metallic domain is larger than the superconducting correlation length of the system suggesting that the observed superconductivity in undoped CeOBiS2 might be due to this embedded metallic phase at the defects. The results also suggest a possible way to develop new systems by manipulation of the defects in these chalcogenides with structural instability.

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Section: Introductionmentioning

confidence: 76%

“…This discrepancy indicates that there may be some new physical mechanism active for the charge transfer between the rare-earth and Bi sites. In this context, the recent observation of superconductivity in undoped CeOBiS 2 15 is highly interesting and needs further investigations.…”

Section: Introductionmentioning

confidence: 99%

Metallic phase in stoichiometric CeOBiS2 revealed by space-resolved ARPES

Sugimoto

Paris

Wakita

et al. 2018

Sci Rep

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“…Figure 5 shows a typical SEM image of R n (O,F)BiS 2 (R n = Nd) single crystals. For comparison, F-free R n OBiS 2 single crystals are grown by CsCl flux [57,58]. Since the heat-treatment temperature for the growth of F-free single crystals is higher than that of R n (O,F)BiS 2 , thus, the quartz tube corrosion from KCl is enhanced at high temperature.…”

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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“…Figure 5 shows a typical SEM image of Rn(O,F)BiS2 (Rn = Nd) single crystals. For comparison, F-free RnOBiS2 single crystals are grown by CsCl flux [57,58]. Since the heat-treatment temperature for the growth of F-free single crystals is higher than that of Rn(O,F)BiS2, thus, the quartz tube corrosion from KCl is enhanced at high temperature.…”

Section: Bis2-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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Superconductivity in CeOBiS2 with cerium valence fluctuation

Cited by 32 publications

References 25 publications

Metallic phase in stoichiometric CeOBiS2 revealed by space-resolved ARPES

Metallic phase in stoichiometric CeOBiS2 revealed by space-resolved ARPES

Crystal Growth Techniques for Layered Superconductors

Crystal Growth Techniques for Layered Superconductors

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