Superconductivity in an infinite-layer nickelate

Li, D.; Lee, Kyuho; Wang, Bai Yang; Osada, Motoki; Crossley, Samuel; Lee, Hye Ryoung; Cui, Yi; Hikita, Yasuyuki; Hwang, Harold Y.

doi:10.1038/s41586-019-1496-5

Cited by 949 publications

(1,048 citation statements)

References 32 publications

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“…The computed a parameter is comparable to that of the oxide nickelates (see e.g. [1]). However, there is a substantial change in the c parameter as a function of the radius of the monovalent A atomacross the series.…”

Section: A Crystal Structuresupporting

confidence: 64%

Infinite-layer fluoro-nickelates as d ⁹ model materials

Bernardini¹,

Olevano

Blase

et al. 2020

J. Phys. Mater.

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We study theoretically the fluoro-nickelate series ANiF2 (A = Li, Na, K, Rb, Cs) in the tetragonal P 4/mmm infinite-layer structure. We use density functional theory to determine the structural parameters and the electronic band structure of these unprecedented compounds. Thus, we predict these materials as model d 9 systems where the Ni 1+ oxidation is realized and the low-energy physics is completely determined by the Ni-3d bands only. Fluoro-nickelates of this class thus offer an ideal platform for the study of intriguing physics that emerges out of the special d 9 electronic configuration, notably high-temperature unconventional superconductivity.

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Section: A Crystal Structuresupporting

confidence: 64%

Infinite-layer fluoro-nickelates as d ⁹ model materials

Bernardini¹,

Olevano

Blase

et al. 2020

J. Phys. Mater.

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“…Possible reasons include the use of different conditions or different parent materials (e.g., bulk ReNiO 3 vs Ruddlesden-Popper layered [35] ). In addition, according to the recent discovery of superconductivity in reduced layered nickelate, such as Nd 0.8 Sr 0.2 NiO 2 , [36] a possible Sr-Sm intermixing in combination with oxygen vacancies at the interface between SrRuO 3 and SmNiO 3 may also influence electron configurations of the nickelate. Nevertheless, even intermixing of Sr and Sm exists to make the initial electronic structure carry a fraction of t e 2g 6 g 0 , [36] the overall physics still holds since the majority part of the initial electronic configuration is t e 2g 6 g 1 .…”

Section: Wwwadvmatde Wwwadvancedsciencenewscommentioning

confidence: 99%

“…In addition, according to the recent discovery of superconductivity in reduced layered nickelate, such as Nd 0.8 Sr 0.2 NiO 2 , [36] a possible Sr-Sm intermixing in combination with oxygen vacancies at the interface between SrRuO 3 and SmNiO 3 may also influence electron configurations of the nickelate. Nevertheless, even intermixing of Sr and Sm exists to make the initial electronic structure carry a fraction of t e 2g 6 g 0 , [36] the overall physics still holds since the majority part of the initial electronic configuration is t e 2g 6 g 1 . In a first order approximation, hybridization variance in different valence states of nickel ion [37,38] would not change the overall metal-insulator-metal phase transition process.…”

Section: Wwwadvmatde Wwwadvancedsciencenewscommentioning

confidence: 99%

Electron‐Doping Mottronics in Strongly Correlated Perovskite

et al. 2019

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Hydrogen (proton) induced switchable multiphase transformations in d-band electron-correlated materials recently opened a new field for exploring merging multifunctional proton-gated electronic devices, [1] synaptic plasticity, [2,3] sensors, [4] and novel energy conversion devices. [5] Compared to other dopant elements, hydrogen is small in radius and has high ionic mobility. [1,[4][5][6] Therefore, the proton distribution is highly adjustable via external electric fields, and the respective tuning of the physical properties of materials is feasible. This is, in particular, the case for the hydrogen-induced sharp transitions in electron orbital configurations and the magnetoelectric/spintronic states for d-band electron-correlated materials, such as SmNiO 3 , [1][2][3][4][5] SrCoO 3−δ , [6] and VO 2 . [7] As a typical example, the hydrogenation of the perovskite-structured SmNiO 3 d-band electron-correlated system results in an abrupt electronic transition of the e g orbital from the electron-itinerant Ni 3+ t e 2g 6 g 1 state to the electron-localized Ni 2+ t e 2g 6 g 2 The discovery of hydrogen-induced electron localization and highly insulating states in d-band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field-controlled electronic devices (e.g., Mottronics). Although a significant understanding of doping-tuned transport properties of single crystalline correlated materials exists, it has remained unclear how dopingcontrolled transport properties behave in the presence of planar defects. The discovery of an unexpected high-concentration doping effect in defective regions is reported for correlated nickelates. It enables electronic conductance by tuning the Fermi-level in Mott-Hubbard band and shaping the lower Hubbard band state into a partially filled configuration. Interface engineering and grain boundary designs are performed for H x SmNiO 3 /SrRuO 3 heterostructures, and a Mottronic device is achieved. The interfacial aggregation of hydrogen is controlled and quantified to establish its correlation with the electrical transport properties. The chemical bonding between the incorporated hydrogen with defective SmNiO 3 is further analyzed by the positron annihilation spectroscopy. The present work unveils new materials physics in correlated materials and suggests novel doping strategies for developing Mottronic and iontronic devices via hydrogen-doping-controlled orbital occupancy in perovskite heterostructures.

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“…For substrates with large in-plane lattice constants such as PMN-PT, MAO and MgO, the thin films show insulating behavior from room temperature. As bulk NSNO has in-plane lattice constants smaller than 4.0 Å, for example, its Nd0.8Sr0.2NiO3 phase has a pseudocubic lattice structure with a ≈ 3.81 Å and the Nd0.8Sr0.2NiO2 phase exhibits a tetragonal structure with a ≈ 3.92 Å [3], NSNO films feel the tensile strain from PMN-PT, MAO and MgO substrates. Consequently, these transport measurements suggest that the electronic state of NSNO films is rather sensitive to substrates and a tensile strain can lead to an insulating state.…”

Section: Experimental Methodsmentioning

confidence: 99%

Absence of superconductivity in Nd0.8Sr0.2NiOx thin films without chemical reduction

et al. 2020

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The recently reported superconductivity 9-15 K in Nd0.8Sr0.2NiO2/SrTiO3heterostructures [Li et al. Nature 572, 624 (2019)] that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3 substrates, has excited an immediate surge of research interest. To explore an alternative physical path instead of chemical reduction for realizing superconductivity in this compound, using pulsed laser deposition, we systematically fabricated 63 Nd0.8Sr0.2NiOx (NSNO) thin films at a wide range of oxygen partial pressures on various different oxide substrates. Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples. With reducing the oxygen content in the NSNO films by lowering the deposition oxygen pressure, the NSNO films are getting more resistive and finally become insulating. Furthermore, we tried to cap a 20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a high oxygen pressure of 150 mTorr to create oxygen vacancies on its surface [Liu et al. Phys. Rev. X 3, 021010 (2013)] and did not succeed in higher conductivity either. Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd0.8Sr0.2NiO2 crystals [Li et al. arXiv: 1911.02420 (2019] suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO3 heterostructures. However, SrTiO3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well, which may thus partially contribute to conductivity [Liu et al. Phys. Rev. Lett. 107, 146802 (2011)].

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Superconductivity in an infinite-layer nickelate

Cited by 949 publications

References 32 publications

Infinite-layer fluoro-nickelates as d ⁹ model materials

Infinite-layer fluoro-nickelates as d ⁹ model materials

Electron‐Doping Mottronics in Strongly Correlated Perovskite

Absence of superconductivity in Nd0.8Sr0.2NiOx thin films without chemical reduction

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Superconductivity in an infinite-layer nickelate

Cited by 949 publications

References 32 publications

Infinite-layer fluoro-nickelates as d 9 model materials

Infinite-layer fluoro-nickelates as d 9 model materials

Electron‐Doping Mottronics in Strongly Correlated Perovskite

Absence of superconductivity in Nd0.8Sr0.2NiOx thin films without chemical reduction

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Infinite-layer fluoro-nickelates as d ⁹ model materials

Infinite-layer fluoro-nickelates as d ⁹ model materials