Charge and Spin Order Dichotomy in 
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 Driven by the Capping Layer

Krieger, Guillaume; Martinelli, Leonardo; Zeng, Shengwei; Chow, L. E.; Kummer, K.; Arpaia, Riccardo; Sala, M. Moretti; Brookes, N. B.; Ariando, Ariando; Viart, N.; Salluzzo, M.; Ghiringhelli, G.; Preziosi, Daniele

doi:10.1103/physrevlett.129.027002

Cited by 77 publications

(33 citation statements)

References 46 publications

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“…The tricomponents are distributed in the lattice with a periodicity determined by the Vo ordering, contributing to a commensurate charge order for this system with a periodicity ( 1 3 , 0, 1 3 ) rlu. This periodicity is strikingly similar to that of the CO reported in IL-nickelate thin films. − This possibly indicates the existence of this phase in IL-nickelate thin films as a defect, and this is further strengthened from recent studies reporting apical oxygen ordering in IL-nickelate thin films that exhibited similar CO. , It questions how intrinsic is the ( 1 3 , 0) rlu CO in IL-NdNiO 2 .…”

Section: Discussionsupporting

confidence: 57%

Valence-Ordered Thin-Film Nickelate with Tri-component Nickel Coordination Prepared by Topochemical Reduction

Raji,

Dong,

Porée

et al. 2024

ACS Nano

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The metal-hydride-based "topochemical reduction" process has produced several thermodynamically unstable phases across various transition metal oxide series with unusual crystal structures and nontrivial ground states. Here, by such an oxygen (de-)intercalation method we synthesis a samarium nickelate with ordered nickel valences associated with tricomponent coordination configurations. This structure, with a formula of Sm 9 Ni 9 O 22 as revealed by four-dimensional scanning transmission electron microscopy (4D-STEM), emerges from the intricate planes of {303} pc ordered apical oxygen vacancies. X-ray spectroscopy measurements and ab initio calculations show the coexistence of square planar, pyramidal, and octahedral Ni sites with mono-, bi-, and tri-valences. It leads to an intense orbital polarization, charge-ordering, and a ground state with a strong electron localization marked by the disappearance of ligand−hole configuration at low temperature. This nickelate compound provides another example of previously inaccessible materials enabled by topotactic transformations and presents an interesting platform where mixed Ni valence can give rise to exotic phenomena.

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Section: Discussionsupporting

confidence: 57%

Valence-Ordered Thin-Film Nickelate with Tri-component Nickel Coordination Prepared by Topochemical Reduction

Raji,

Dong,

Porée

et al. 2024

ACS Nano

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“…[20] changing the Ni valence at these sites. The charge distribution is reflected in the spectroscopic studies, XAS showing a mixed valence and RIXS experiments already demonstrating a broken symmetry of the uc‐NNO2 [ 5 ] in reciprocal space. Since, now we have an understanding of the real space location of these stripes, HAXPES and monochromated STEM‐EELS can probe the concomitant charge modulation as well.…”

Section: Resultsmentioning

confidence: 99%

“…The particular way in which nickelates are prepared, that is presence/absence of a capping layer, combined with the subtle control of the crystal structure modification during the reduction process, is pivotal to attaining the zero-resistance state. [2][3][4] Apart from superconductivity, recent studies have also revealed the existence of charge ordering phenomena and magnetic excitations in IL-nickelate thin films, [5][6][7][8] the amplitudes of which mostly depend upon the particular sample preparation, that is presence/absence of a SrTiO 3 (STO) capping-layer and doping level. In particular, charge order (CO) has been observed in uncapped-IL NdNiO 2 samples and it is not much pronounced in the capped ones, which on the contrary host dispersing magnetic excitation with a bandwidth of circa 200 meV.…”

Section: Introductionmentioning

confidence: 99%

Charge Distribution across Capped and Uncapped Infinite‐Layer Neodymium Nickelate Thin Films

Raji,

Krieger,

Viart

et al. 2023

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Charge ordering (CO) phenomena have been widely debated in strongly‐correlated electron systems mainly regarding their role in high‐temperature superconductivity. Here, the structural and charge distribution in NdNiO2 thin films prepared with and without capping layers, and characterized by the absence and presence of CO are elucidated. The microstructural and spectroscopic analysis is done by scanning transmission electron microscopy‐electron energy loss spectroscopy (STEM‐EELS) and hard X‐ray photoemission spectroscopy (HAXPES). Capped samples show Ni1+, with an out‐of‐plane (o‐o‐p) lattice parameter of around 3.30 Å indicating good stabilization of the infinite‐layer structure. Bulk‐sensitive HAXPES on Ni‐2p shows weak satellite features indicating large charge‐transfer energy. The uncapped samples evidence an increase of the o‐o‐p parameter up to 3.65 Å on the thin film top with a valence toward Ni2+ in this region. Here, 4D‐STEM demonstrates (303)‐oriented stripes which emerge from partially occupied apical oxygen. Those stripes form quasi‐2D coherent domains viewed as rods in the reciprocal space with Δqz ≈ 0.24 reciprocal lattice units (r.l.u.) extension located at Q = () and () r.l.u. The stripes associated with oxygen re‐intercalation concomitant with hole doping suggest a possible link to the previously reported CO in infinite‐layer nickelate thin films.

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“…[ 44 ] Other than the enhanced crystallinity, the improved T c together with 2D character of superconductivity observed here may be related to the increased c lattice constants of La‐based nickelates compared to Nd‐based ones. [ 33,54,55 ] However, further strain‐dependent measurements on nickelate films are needed to confirm the impact of c lattice constants on T c and dimensionality of superconductivity, which is beyond the scope of the present work.…”

Section: Resultsmentioning

confidence: 99%

Evidence for Anisotropic Superconductivity Beyond Pauli Limit in Infinite‐Layer Lanthanum Nickelates

Sun

Liu

et al. 2023

Advanced Materials

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After being expected to be a promising analog to cuprates for decades, superconductivity has recently been discovered in infinite‐layer nickelates, providing new opportunities to explore mechanisms of high‐temperature superconductivity. However, in sharp contrast to the single‐band and anisotropic superconductivity in cuprates, nickelates exhibit a multi‐band electronic structure and an unexpected isotropic superconductivity as reported recently, which challenges the cuprate‐like picture in nickelates. Here, it is shown that strong anisotropic magnetotransport behaviors exist in La‐based nickelate films with enhanced crystallinity and superconductivity ( = 18.8 K, = 16.5 K). The upper critical fields are anisotropic and violate the estimated Bardeen–Cooper–Schrieffer (BCS) Pauli limit () for in‐plane magnetic fields. Moreover, the anisotropic superconductivity is further manifested by the cusp‐like peak of the angle‐dependent Tc and the vortex motion anisotropy under external magnetic fields.

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Charge and Spin Order Dichotomy in NdNiO2 Driven by the Capping Layer

Cited by 77 publications

References 46 publications

Valence-Ordered Thin-Film Nickelate with Tri-component Nickel Coordination Prepared by Topochemical Reduction

Valence-Ordered Thin-Film Nickelate with Tri-component Nickel Coordination Prepared by Topochemical Reduction

Charge Distribution across Capped and Uncapped Infinite‐Layer Neodymium Nickelate Thin Films

Evidence for Anisotropic Superconductivity Beyond Pauli Limit in Infinite‐Layer Lanthanum Nickelates

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