Iron chalcogenide superconductors at high magnetic fields

Titanium oxides have many fascinating optical and electrical properties, such as the superconductivity at 2 K in cubic titanium monoxide (TiO) polycrystalline bulk. However, the lack of TiO single crystals or epitaxial films has prevented systematic investigations on its superconductivity. Here, we report the basic superconductivity characterizations of cubic TiO films epitaxially grown on (0001)-oriented α-Al 2 O 3 substrates. The magnetic and electronic transport measurements confirmed that TiO is a type-II superconductor and the recorded high T c is about 7.4 K. The lower critical field (H c1 ) at 1.9 K, the extrapolated upper critical field H c2 (0), and coherence length are about 18 Oe, 13.7 T, and 4.9 nm, respectively. With increasing pressure, the value of T c shifts to lower temperature while the normal state resistivity increases. Our results on the superconducting TiO films confirm the strategy to achieve higher T c in the epitaxial films, which may be helpful for finding more superconducting materials in various related systems.

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“…S4 for the detailed information). 34,35 The upper critical field vs. temperature curves can be well fitted by: 36…”

Section: Resultsmentioning

confidence: 99%

Enhanced superconductivity in TiO epitaxial thin films

et al. 2017

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“…At ambient pressure, T c reaches as high as 55 K and 56 K in SmO 1−x F x FeAs and Sr 1−x Sm x FFeAs, respectively [31,32]. Since their discovery, iron-selenide SCs have been found to provide a strong platform for the investigation of their high-T c superconductivity, since they possess a simple structure, are nontoxic, and may be fabricated via numerous synthesis methods [2,18,33,34]. The simplest tetragonal β-Fe 1+δ Se (11-system) has T c ≈ 8.5 K at ambient pressure and is sensitive to chemical and physical pressure effects [35].…”

Section: Introductionmentioning

confidence: 99%

(Li1−xFex)OHFeSe Superconductors: Crystal Growth, Structure, and Electromagnetic Properties

2017

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This review focuses on the growth of high-quality (Li 1−x Fe x )OHFeSe single crystals by a hydrothermal method using floating-zone-grown A x Fe 2−y Se 2 (A = K, Rb, and Cs) as precursors. The structure, superconductivity, and magnetic behavior of the obtained crystals are highly influenced by the growth conditions, such as time, temperature, and composition. A phase diagram with temperature against the c-lattice constant is summarized including the antiferromagnetic spin density wave, superconducting, and paramagnetic phases.

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“…The inversion of anisotropy of H c2 (T ) was also associated with equatorial nodes in a single band order parameter 21 Fig. 4 can hardly be explained by the enhancement of H c2 by the spin orbital effects 23,24 which would require unrealistically large spin-orbital coupling constants 28,29 . We suggest that the behavior of H c2 (T ) shown in Fig.…”

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confidence: 99%