Synthesis of infinite-layer LaNiO2 films by metal organic decomposition

Kaneko, D.; Yamagishi, K.; Tsukada, A.; Manabe, Takaaki; Naito, Makio

doi:10.1016/j.physc.2009.05.104

Cited by 42 publications

(35 citation statements)

References 9 publications

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“…1(b) is strongly anisotropic (maximally so), similar to that obtained previously [2] for d 9 LaNiO 2 , where large U drove the system toward an unexpected d 8 configuration. U = 6-8 eV was judged to be too large for conducting LaNiO 2 , which is observed to be conducting and would have a more strongly screened (smaller) value of U [29].…”

Section: Correlation and Spin Polarization: The Odsmentioning

confidence: 98%

Proposed ordering of textured spin singlets in a bulk infinite-layer nickelate

Jin

Pickett

Lee

2020

Phys. Rev. Research

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The infinite-layer structure nickelate Ba 2 NiO 2 (AgSe) 2 (BNOAS) with d 8 Ni ions and a peculiar susceptibility χ (T), synthesized at high pressure, is studied with correlated density functional methods. The overriding feature of the calculations is a violation of Hund's rule coupled with complete but unconventional spin-orbital polarization, leading to an unexpected low-spin 1 B 1 , "off-diagonal singlet" textured by an internal orbital structure of compensating d ↑ x 2 −y 2 and d ↓ z 2 spins. This unconventional configuration has a lower energy than conventional high-spin or low-spin alternatives. An electronic transition is obtained at a critical Ni-O separation d Ni-O c = 2.03 Å, which corresponds closely to the observed critical value of 2.00-2.05 Å, above which Ni becomes magnetic in square planar NiO 2 compounds. We propose scenarios for the signature of magnetic reconstruction in χ (T) at T m = 130 K without any Curie-Weiss background (no moment) that invokes ordering of Ni d 8 moieties that are largely this generalized Kondo singlet. Because hole states are primarily Se 4p rather than O 2p, the usual issue of Mott insulator versus charge transfer insulator is supplanted by a character in which electrons and holes are separated in real space. The underlying physics of this system is modeled by a Kondo sieve spin model (two-dimensional Kondo necklace) of a "Kondo" d z 2 spin on each site, coupled to a d x 2 −y 2 spin that is itself strongly coupled to neighboring like-spins within the layer. The observed magnetic order places BNOAS below the quantum critical point of the Kondo sieve model, providing a realization of the long-range ordered near-singlet weak antiferromagnetic phase. We propose electron doping experiments that would drive the system toward a d 9−δ configuration and possible superconductivity with a similarity to the recently reported hole-doped infinite-layer cuprate Ba 2 CuO 3.2 that superconducts at 73 K.

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Section: Correlation and Spin Polarization: The Odsmentioning

confidence: 98%

Proposed ordering of textured spin singlets in a bulk infinite-layer nickelate

Jin

Pickett

Lee

2020

Phys. Rev. Research

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“…With the same infinite-layer structure as CaCuO 2 (CCO), which superconducts up to 110 K when doped [27], NNO displays several differences with CCO. Undoped NNO is conducting; CCO is insulating; CCO orders antiferromagnetically, whereas no signature of order is seen in NNO (and its isoelectronic but nonsuperconducting sister LaNiO 2 (LNO) [28][29][30][31]) and there is no sign of heavy-fermion screening of Ni moments. CCO and NNO have a common d 9 (formal) configuration (one hole) on the transition metal ion, however, NNO persists as (poorly) conducting to low temperature.…”

Section: Introductionmentioning

confidence: 99%

Fluctuation-frustrated flat band instabilities in NdNiO2

Choi

Pickett

Lee

2020

Phys. Rev. Research

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The discovery that Nd 1−x Sr x NiO 2 , with the CaCuO 2 infinite-layer structure, superconducts up to 15 K around the hole-doping level x = 0.2 raises the crucial question of its fundamental electronic and magnetic processes. The unexplained basic feature that we address is that, for x = 0 and as opposed to strongly antiferromagnetic (AFM) CaCuO 2 , NdNiO 2 with the same structure and formal d 9 configuration does not undergo AFM order. We study this issue not in the conventional manner, as energetically unfavored or as frustrated magnetic order, but as an instability of the AFM phase itself. We are able to obtain the static AFM ordered state, but find that a flat band, one-dimensional-like van Hove singularity (vHs) is pinned to the Fermi level. This situation is unusual in a non-half-filled, effectively two-band system. The vHs makes the AFM phase unstable to spindensity disproportionation, breathing, and half-breathing lattice distortions, and (innate or parasitic) chargedensity disproportionation. These flat band instabilities, distant relatives of single-band cuprate models, thereby inhibit but do not eliminate incipient AFM tendencies at low temperature. The primary feature is that a pair of active bands (d x 2 −y 2 , d z 2) eliminate half-filled physics and, due to instabilities, preclude the AFM phase seen in CaCuO 2. This strongly AFM correlated, conducting spin-liquid phase with strong participation of the Ni d z 2 orbital forms the platform for superconductivity in NdNiO 2 .

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“…In a more bulk-like crystal, no superconductivity was reported for Nd 0.8 Sr 0.2 NiO 2 [5]; neither is NdNiO 2 superconducting [1] but shows a resistivity upturn toward low temperatures. Another nickelate, LaNiO 2 , is also isostructural and isovalent, but is a (bad) metal [6] with no superconductivity nor antiferromagnetism [7].…”

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confidence: 99%

Topotactic Hydrogen in Nickelate Superconductors and Akin Infinite-Layer Oxides ABO2

et al. 2020

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Superconducting nickelates appear to be difficult to synthesize. Since the chemical reduction of ABO3 (A: rare earth; B transition metal) with CaH2 may result in both, ABO2 and ABO2H, we calculate the topotactic H binding energy by density functional theory (DFT). We find intercalating H to be energetically favorable for LaNiO2 but not for Sr-doped NdNiO2. This has dramatic consequences for the electronic structure as determined by DFT+dynamical mean field theory: that of 3d 9 LaNiO2 is similar to (doped) cuprates, 3d 8 LaNiO2H is a two-orbital Mott insulator. Topotactic H might hence explain why some nickelates are superconducting and others are not.

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Synthesis of infinite-layer LaNiO2 films by metal organic decomposition

Cited by 42 publications

References 9 publications

Proposed ordering of textured spin singlets in a bulk infinite-layer nickelate

Proposed ordering of textured spin singlets in a bulk infinite-layer nickelate

Fluctuation-frustrated flat band instabilities in NdNiO2

Topotactic Hydrogen in Nickelate Superconductors and Akin Infinite-Layer Oxides ABO2

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