Superconductivity at 52 K in hydrogen-substituted LaFeAsO1-xHx under high pressure

Takahashi, Hiroki; Soeda, Hideo; Nukii, M.; Kawashima, Chizuru; Nakanishi, Toru; Iimura, Soshi; Muraba, Yoshinori; Matsuishi, Satoru; Hosono, Hideo

doi:10.1038/srep07829

Cited by 36 publications

(42 citation statements)

References 25 publications

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“…For each value of x , the lattice parameters a and c decrease monotonically up to ~8 GPa with linear compressibilities of k a = 2.54–2.62 × 10 −3 GPa −1 and k c = 5.50–5.64 × 10 −3 GPa −1 . These values agree with previously reported linear compressibilities of LaFeAsO 0.72 H 0.18 and SmFeAsO1318. k a and k c for all LaFeAsO 1− x H x complexes are less than and similar to the respective corresponding values of 3.5 × 10 −3 GPa −1 and 5.4 × 10 −3 GPa −1 for BaFe 2 As 2 19.…”

Section: Resultssupporting

confidence: 91%

“…Takahashi et al . have recently demonstrated that the application of pressure on LaFeAsO 0.72 H 0.18 induced a notable enhancement of the T c from 18 K at ambient pressure to 52 K at 6 GPa13. Interestingly, the maximum T c of LaFeAsO 0.72 H 0.18 under pressure was similar to that of Sm1111 (55 K), the highest known T c among iron-based superconductors14.…”

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confidence: 90%

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Pressure effect on iron-based superconductor LaFeAsO1−xHx: Peculiar response of 1111-type structure

Kobayashi

Yamaura

Iimura

et al. 2016

Sci Rep

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A systematic study of the crystal structure of a layered iron oxypnictide LaFeAsO1−xHx as a function of pressure was performed using synchrotron X-ray diffraction. This compound exhibits a unique phase diagram of two superconducting phases and two parent phases. We established that the As–Fe–As angle of the FeAs4 tetrahedron widens on the application of pressure due to the interspace between the layers being nearly infilled by the large La and As atoms. Such rarely observed behaviour in iron pnictides implies that the FeAs4 coordination deviates from the regular tetrahedron in the present systems. This breaks a widely accepted structural guide that the superconductivity favours the regular tetrahedron, albeit the superconducting transition temperature (Tc) increases from 18 K at ambient pressure to 52 K at 6 GPa for x = 0.2. In the phase diagram, the second parent phase at x ~ 0.5 is suppressed by pressure as low as ~1.5 GPa in contrast to the first parent phase at x ~ 0, which is robust against pressure. We suggest that certain spin-fluctuation from the second parent phase is strongly related to high-Tc under pressure.

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Section: Resultssupporting

confidence: 91%

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confidence: 90%

Pressure effect on iron-based superconductor LaFeAsO1−xHx: Peculiar response of 1111-type structure

Kobayashi

Yamaura

Iimura

et al. 2016

Sci Rep

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“…The electron doping via hydride ion substitution into the oxygen site results in the suppression of AFM (AFM1) ordering and subsequently the emergence of a superconducting phase for the electron doping range of 0.05 ≤ e − /Fe ≤ 0.45 (11,12). The optimum T c , which depends strikingly on the RE size, is 36 K for RE = La, and 56 K for Sm or Gd, consistent with the observation that the application of physical pressure to La-1111 can enhance its T c from 36 K to 52 K (12,13). In the overdoped regime of La-1111 (electron doping levels ≥ 0.40e − /Fe), another long-range AFM ordering (AFM2) was observed by the neutron powder diffraction (NPD) and muon spin relaxation techniques (14).…”

supporting

confidence: 64%

Large-moment antiferromagnetic order in overdoped high- T _c superconductor ¹⁵⁴ SmFeAsO _{1−
x} D _x

Iimura

Okanishi

Matsuishi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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In iron-based superconductors, high critical temperature (T c ) superconductivity over 50 K has only been accomplished in electron-doped hREFeAsO (hRE is heavy rare earth (RE) element). Although hREFeAsO has the highest bulk T c (58 K), progress in understanding its physical properties has been relatively slow due to difficulties in achieving high-concentration electron doping and carrying out neutron experiments. Here, we present a systematic neutron powder diffraction study of 154 SmFeAsO 1−x D x , and the discovery of a long-range antiferromagnetic ordering with x ≥ 0.56 (AFM2) accompanying a structural transition from tetragonal to orthorhombic. Surprisingly, the Fe magnetic moment in AFM2 reaches a magnitude of 2.73 μ B /Fe, which is the largest in all nondoped iron pnictides and chalcogenides. Theoretical calculations suggest that the AFM2 phase originates in kinetic frustration of the Fe-3d xy orbital, in which the nearest-neighbor hopping parameter becomes zero. The unique phase diagram, i.e., highest-T c superconducting phase adjacent to the strongly correlated phase in electron-overdoped regime, yields important clues to the unconventional origins of superconductivity.high-T c superconductivity | neutron scattering | oxyhydrides | iron-based superconductors | antiferromagnetism C arrier doping is a critical parameter that governs the electronic correlations and ground states in high-T c superconductors. Electronic phase diagrams depicting the evolution of the ground state with doping level not only deepen our understanding of the mechanism of superconductivity but help us extract common trends across different superconducting materials. Until recently, two electronic phases were believed to play a vital role in iron-based superconductivity, i.e., a stripe or double-stripe-type antiferromagnetic (AFM) ordering at a nondoped Fe-3d 6 state and a Mott insulator at a hole-doped Fe-3d 5 state (1-3). The former phase is observed at ambient pressure for the arsenides and telluride, while under high pressures for the selenides, and the AFM fluctuations are a promising candidate for the pairing glue leading to superconductivity (4, 5). On the other hand, the latter picture, confirmed recently in effectively hole-doped Na(Fe 3+ 0.5 Cu + 0.5 )As (6), explains the asymmetric response of the T c and electron correlation to hole and electron doping, where the hole doping (electron doping) into the Fe-3d 6 state tends to enhance (reduce) the T c and the degree of electron correlation, because the system approaches (goes away from) the half-filled Fe-3d 5 state (2).However, these two prevailing scenarios were challenged recently by observations of the behavior of heavily electron-doped FeSe (11-type) and REFeAsO (1111-type), where the T c and electron correlation strength are enhanced rather than weakened with electron doping. In the first of these systems, a quite high T c in the range of 35 K to 41 K was observed, for the electron-doped FeSe using an electric double-layer transistor, which climbs to 46 K to 48 K for ...

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“…[12][13][14] Superconductivity is induced when these transitions are suppressed, and the critical temperature (Tc) is 55 K for Ln = Sm; this is the highest reported value for iron pnictides. 9,15 Although various methods for suppressing these transitions and tuning their physical properties have been proposed, 1,[15][16][17][18][19][20][21][22] electron doping by hydride substitution (O 2− → H − + e − ) 23,24 and the introduction of oxygen vacancies (O 2− → Vo + 2e − ), [25][26][27] both of which can be achieved using high-pressure synthesis, are recognized as techniques that can be used to attain the highest Tc superconductivity. A phase diagram of the critical temperature vs dopant concentration is a fundamental map that connects physical properties to electronic structures.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen-Substituted Superconductors SmFeAsO_1–xH_x Misidentified As Oxygen-Deficient SmFeAsO_1–x

et al. 2015

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We investigated the preferred electron dopants at the oxygen sites of 1111-type SmFeAsO by changing the atmospheres around the precursor with the composition of Sm:Fe:As:O = 1:1:1:1-x in high-pressure synthesis. Under H2O and H2 atmospheres, hydrogens derived from H2O or H2 molecules were introduced into the oxygen sites as a hydride ion, and SmFeAsO1−xHx was obtained. However, when the H2O and H2 sources were removed from the synthetic process, nearly stoichiometric SmFeAsO was obtained and the maximum amount of oxygen vacancies introduced remained x = 0.05(4). Density functional theory calculations indicated that substitution of hydrogen in the form of H − is more stable than the formation of an oxygen vacancy at the oxygen site of SmFeAsO.These results strongly imply that oxygen-deficient SmFeAsO1−x reported previously is SmFeAsO1−xHx with hydride ion incorporated unintentionally during high-pressure synthesis.

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Superconductivity at 52 K in hydrogen-substituted LaFeAsO1-xHx under high pressure

Cited by 36 publications

References 25 publications

Pressure effect on iron-based superconductor LaFeAsO1−xHx: Peculiar response of 1111-type structure

Pressure effect on iron-based superconductor LaFeAsO1−xHx: Peculiar response of 1111-type structure

Large-moment antiferromagnetic order in overdoped high- T _c superconductor ¹⁵⁴ SmFeAsO _{1−
x} D _x

Hydrogen-Substituted Superconductors SmFeAsO_1–xH_x Misidentified As Oxygen-Deficient SmFeAsO_1–x

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Superconductivity at 52 K in hydrogen-substituted LaFeAsO1-xHx under high pressure

Cited by 36 publications

References 25 publications

Pressure effect on iron-based superconductor LaFeAsO1−xHx: Peculiar response of 1111-type structure

Pressure effect on iron-based superconductor LaFeAsO1−xHx: Peculiar response of 1111-type structure

Large-moment antiferromagnetic order in overdoped high- T c superconductor 154 SmFeAsO 1− x D x

Hydrogen-Substituted Superconductors SmFeAsO1–xHx Misidentified As Oxygen-Deficient SmFeAsO1–x

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Product

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Large-moment antiferromagnetic order in overdoped high- T _c superconductor ¹⁵⁴ SmFeAsO _{1−
x} D _x

Hydrogen-Substituted Superconductors SmFeAsO_1–xH_x Misidentified As Oxygen-Deficient SmFeAsO_1–x