skip to main content

This content will become publicly available on December 1, 2023

Title: Antiferromagnetic insulating state in layered nickelates at half filling
Abstract We provide a set of computational experiments based on ab initio calculations to elucidate whether a cuprate-like antiferromagnetic insulating state can be present in the phase diagram of the low-valence layered nickelate family (R $$_{n+1}$$ n + 1 Ni $$_n$$ n O $$_{2n+2}$$ 2 n + 2 , R= rare-earth, $$n=1-\infty$$ n = 1 - ∞ ) in proximity to half-filling. It is well established that at $$d^9$$ d 9 filling the infinite-layer ( $$n=\infty$$ n = ∞ ) nickelate is metallic, in contrast to cuprates wherein an antiferromagnetic insulator is expected. We show that for the Ruddlesden-Popper (RP) reduced phases of the series (finite n ) an antiferromagnetic insulating ground state can naturally be obtained instead at $$d^9$$ d 9 filling, due to the spacer RO $$_2$$ 2 fluorite slabs present in their structure that block the c -axis dispersion. In the $$n=\infty$$ n = ∞ nickelate, the same type of solution can be derived if the off-plane R-Ni coupling is suppressed. We show how this can be achieved if a structural element that cuts off the c -axis dispersion is introduced (i.e. vacuum in a monolayer of RNiO $$_2$$ 2 , or a blocking layer in multilayers more » formed by (RNiO $$_2$$ 2 ) $$_1$$ 1 /(RNaO $$_2$$ 2 ) $$_1$$ 1 ). « less
Authors:
; ; ;
Award ID(s):
2045826
Publication Date:
NSF-PAR ID:
10382300
Journal Name:
Scientific Reports
Volume:
12
Issue:
1
ISSN:
2045-2322
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract We study several model-theoretic aspects of W $$^*$$ ∗ -probability spaces, that is, $$\sigma $$ σ -finite von Neumann algebras equipped with a faithful normal state. We first study the existentially closed W $$^*$$ ∗ -spaces and prove several structural results about such spaces, including that they are type III $$_1$$ 1 factors that tensorially absorb the Araki–Woods factor $$R_\infty $$ R ∞ . We also study the existentially closed objects in the restricted class of W $$^*$$ ∗ -probability spaces with Kirchberg’s QWEP property, proving that $$R_\infty $$ R ∞ itself is such an existentially closed space in this class. Our results about existentially closed probability spaces imply that the class of type III $$_1$$ 1 factors forms a $$\forall _2$$ ∀ 2 -axiomatizable class. We show that for $$\lambda \in (0,1)$$ λ ∈ ( 0 , 1 ) , the class of III $$_\lambda $$ λ factors is not $$\forall _2$$ ∀ 2 -axiomatizable but is $$\forall _3$$ ∀ 3 -axiomatizable; this latter result uses a version of Keisler’s Sandwich theorem adapted to continuous logic. Finally, we discuss some results around elementary equivalence of III $$_\lambda $$ λ factors. Using a result of Boutonnet, Chifan, and Ioana,more »we show that, for any $$\lambda \in (0,1)$$ λ ∈ ( 0 , 1 ) , there is a family of pairwise non-elementarily equivalent III $$_\lambda $$ λ factors of size continuum. While we cannot prove the same result for III $$_1$$ 1 factors, we show that there are at least three pairwise non-elementarily equivalent III $$_1$$ 1 factors by showing that the class of full factors is preserved under elementary equivalence.« less
  2. All-solid-state batteries (ASSBs) have garnered increasing attention due to the enhanced safety, featuring nonflammable solid electrolytes as well as the potential to achieve high energy density. 1 The advancement of the ASSBs is expected to provide, arguably, the most straightforward path towards practical, high-energy, and rechargeable batteries based on metallic anodes. 1 However, the sluggish ion transmission at the cathode-electrolyte (solid/solid) interface would result in the high resistant at the contact and limit the practical implementation of these all solid-state materials in real world batteries. 2 Several methods were suggested to enhance the kinetic condition of the ion migration between the cathode and the solid electrolyte (SE). 3 A composite strategy that mixes active materials and SEs for the cathode is a general way to decrease the ion transmission barrier at the cathode-electrolyte interface. 3 The active material concentration in the cathode is reduced as much as the SE portion increases by which the energy density of the ASSB is restricted. In addition, the mixing approach generally accompanies lattice mismatches between the cathode active materials and the SE, thus providing only limited improvements, which is imputed by random contacts between the cathode active materials and the SE during the mixingmore »process. Implementing high-pressure for the electrode and electrolyte of ASSB in the assembling process has been verified is a but effective way to boost the ion transmission ability between the cathode active materials and the SE by decreasing the grain boundary impedance. Whereas the short-circuit of the battery would be induced by the mechanical deformation of the electrolyte under high pressure. 4 Herein, we demonstrate a novel way to address the ion transmission problem at the cathode-electrolyte interface in ASSBs. Starting from the cathode configuration, the finite element method (FEM) was employed to evaluate the current concentration and the distribution of the space charge layer at the cathode-electrolyte interface. Hierarchical three-dimensional (HTD) structures are found to have a higher Li + transfer number (t Li+ ), fewer free anions, and the weaker space-charge layer at the cathode-electrolyte interface in the resulting FEM simulation. To take advantage of the HTD structure, stereolithography is adopted as a manufacturing technique and single-crystalline Ni-rich (SCN) materials are selected as the active materials. Next, the manufactured HTD cathode is sintered at 600 °C in an N 2 atmosphere for the carbonization of the resin, which induces sufficient electronic conductivity for the cathode. Then, the gel-like Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP) precursor is synthesized and filled into the voids of the HTD structure cathode sufficiently. And the filled HTD structure cathodes are sintered at 900 °C to achieve the crystallization of the LATP gel. Scanning transmission electron microscopy (STEM) is used to unveil the morphology of the cathode-electrolyte interface between the sintered HTD cathode and the in-situ generated electrolyte (LATP). A transient phase has been found generated at the interface and matched with both lattices of the SCN and the SE, accelerating the transmission of the Li-ions, which is further verified by density functional theory calculations. In addition, Electron Energy Loss Spectroscopy demonstrates the preserved interface between HTD cathode and SEs. Atomic force microscopy is employed to measure the potential image of the cross-sectional interface by the peak force tapping mode. The average potential of modified samples is lower than the sample that mix SCN and SEs simply in the 2D planar structure, which confirms a weakened space charge layer by the enhanced contact capability as well as the ion transmission ability. To see if the demonstrated method is universally applicable, LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is selected as the cathode active material and manufactured in the same way as the SCN. The HTD cathode based on NCM811 exhibits higher electrochemical performance compared with the reference sample based on the 2D planar mixing-type cathode. We believe such a demonstrated universal strategy provides a new guideline to engineer the cathode/electrolyte interface by revolutionizing electrode structures that can be applicable to all-solid-state batteries. Figure 1. Schematic of comparing of traditional 2D planar cathode and HTD cathode in ASSB Tikekar, M. D. , et al. , Nature Energy (2016) 1 (9), 16114 Banerjee, A. , et al. , Chem Rev (2020) 120 (14), 6878 Chen, R. , et al. , Chem Rev (2020) 120 (14), 6820 Cheng, X. , et al. , Advanced Energy Materials (2018) 8 (7) Figure 1« less
  3. Abstract

    The status of nickelate superconductors in relation to cuprate high temperature superconductors is one of the concepts being discussed in high temperature superconductivity in correlated transition metal oxides. New additions to the class of infinite layer nickelates can provide essential input relating to connections or distinctions. A recently synthesized compound Ba2NiO2(AgSe)2, which contains isolated ‘infinite layer’ NiO2planes, may lead to new insights. Our investigations have discovered that, at density functional theory mean field level, the ground state consists of an unusualegsinglet on the Ni2+ion arising from large but separate Mott insulating gaps in bothegorbitals, but with different, anti-Hund’s, spin directions of their moments. This textured singlet incorporates at the least new physics, and potentially a new platform for nickelate superconductivity, which might be of an unconventional form for transition metal oxides due to the unconventional undoped state. We include in this paper a comparison of electronic structure parameters of Ba2NiO2(AgSe)2with a better characterized infinite layer nickelate LaNiO2. We provide more analysis of thed8anti-Hund’s singlet that emerges in this compound, and consider a minimally correlated wavefunction for this singlet in an itinerant background, and begin discussion of excitations—real or virtual—that may figuremore »into new electronic phases.

    « less
  4. The recent observation of superconductivity in N d 0.8 S r 0.2 N i O 2 has raised fundamental questions about the hierarchy of the underlying electronic structure. Calculations suggest that this system falls in the Mott–Hubbard regime, rather than the charge-transfer configuration of other nickel oxides and the superconducting cuprates. Here, we use state-of-the-art, locally resolved electron energy-loss spectroscopy to directly probe the Mott–Hubbard character of N d 1 − x S r x N i O 2 . Upon doping, we observe emergent hybridization reminiscent of the Zhang–Rice singlet via the oxygen-projected states, modification of the Nd 5d states, and the systematic evolution of Ni 3d hybridization and filling. These experimental data provide direct evidence for the multiband electronic structure of the superconducting infinite-layer nickelates, particularly via the effects of hole doping on not only the oxygen but also nickel and rare-earth bands.
  5. A gr e at d e al of i nt er e st s urr o u n d s t h e u s e of tr a n s cr a ni al dir e ct c urr e nt sti m ul ati o n (t D C S) t o a u g m e nt c o g niti v e tr ai ni n g. H o w e v er, eff e ct s ar e i n c o n si st e nt a cr o s s st u di e s, a n d m et aa n al yti c e vi d e n c e i s mi x e d, e s p e ci all y f o r h e alt h y, y o u n g a d ult s. O n e m aj or s o ur c e of t hi s i n c o n si st e n c y i s i n di vi d u al diff er e n c e s a m o n g t h e pmore »arti ci p a nt s, b ut t h e s e diff er e n c e s ar e r ar el y e x a mi n e d i n t h e c o nt e xt of c o m bi n e d tr ai ni n g/ sti m ul ati o n st u di e s. I n a d diti o n, it i s u n cl e ar h o w l o n g t h e eff e ct s of sti m ul ati o n l a st, e v e n i n s u c c e s sf ul i nt er v e nti o n s. S o m e st u di e s m a k e u s e of f oll o w- u p a s s e s s m e nt s, b ut v er y f e w h a v e m e a s ur e d p erf or m a n c e m or e t h a n a f e w m o nt hs aft er a n i nt er v e nti o n. H er e, w e utili z e d d at a fr o m a pr e vi o u s st u d y of t D C S a n d c o g niti v e tr ai ni n g [ A u, J., K at z, B., B u s c h k u e hl, M., B u n arj o, K., S e n g er, T., Z a b el, C., et al. E n h a n ci n g w or ki n g m e m or y tr ai ni n g wit h tr a n scr a ni al dir e ct c urr e nt sti m ul ati o n. J o u r n al of C o g niti v e N e u r os ci e n c e, 2 8, 1 4 1 9 – 1 4 3 2, 2 0 1 6] i n w hi c h p arti ci p a nts tr ai n e d o n a w or ki n g m e m or y t as k o v er 7 d a y s w hil e r e c ei vi n g a cti v e or s h a m t D C S. A n e w, l o n g er-t er m f oll o w- u p t o a ss es s l at er p erf or m a n c e w a s c o n d u ct e d, a n d a d diti o n al p arti ci p a nt s w er e a d d e d s o t h at t h e s h a m c o n diti o n w a s b ett er p o w er e d. W e a s s e s s e d b a s eli n e c o g niti v e a bilit y, g e n d er, tr ai ni n g sit e, a n d m oti v ati o n l e v el a n d f o u n d si g nifi c a nt i nt er a cti o ns b et w e e n b ot h b as eli n e a bilit y a n d m oti v ati o n wit h c o n diti o n ( a cti v e or s h a m) i n m o d els pr e di cti n g tr ai ni n g g ai n. I n a d diti o n, t h e i m pr o v e m e nt s i n t h e a cti v e c o nditi o n v er s u s s h a m c o n diti o n a p p e ar t o b e st a bl e e v e n a s l o n g a s a y e ar aft er t h e ori gi n al i nt er v e nti o n. ■« less