Orbital Engineering in Symmetry-Breaking Polar Heterostructures

Disa, Ankit; Kumah, Divine P.; Malashevich, Andrei; Chen, Hanghui; Arena, D. A.; Specht, E. D.; Ismail‐Beigi, Sohrab; Walker, Frederick J.; Ahn, Charles

doi:10.1103/physrevlett.114.026801

Cited by 153 publications

(175 citation statements)

References 51 publications

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“…16,17,[19][20][21][22][23][24][25][26][27][28][29][30][31] Many of the physical properties of metal oxides are sensitive to the presence of oxygen vacancies. In stoichiometric bulk LaNiO 3 , Ni ion assumes 3+ charge state, while oxygen deficiency can result in the creation of Ni 2+ ions, significantly affecting conductivity and MIT.…”

Section: -18mentioning

confidence: 99%

First-principles study of oxygen-deficientLaNiO3structures

Malashevich

Ismail‐Beigi

2015

Phys. Rev. B

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We describe the results of first-principles calculations of the properties of oxygen vacancies in LaNiO3. We consider isolated oxygen vacancies, pairs of vacancies, and vacancies at finite concentrations that form oxygen-deficient phases of LaNiO3. The key electronic structure question we address is whether and to what extent an oxygen vacancy acts as an electron donor to the Fermi level (mobile and conducting electronic states). More generally, we describe how one can quantify, based on electronic structure calculations, the extent to which a localized point defect in a metallic system donates electrons to the Fermi level compared to trapping electrons in localized defect states. For LaNiO3, we find that an oxygen vacancy does not create mobile carrier but instead makes the two Ni sites adjacent to it turn into Ni 2+ cations. Energetically, we compute the formation energy and diffusion barrier for oxygen vacancies. Structurally, we show that pair of vacancies prefer to form on opposite sides of a Ni cation, aligning along a pseudocubic axis. For finite concentrations of vacancies, we compute the dependence of the LaNiO3 lattice parameters on the vacancy concentration to provide reliable data for experimental determination of oxygen content in LaNiO3 and LaNiO3 thin films.

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Section: -18mentioning

confidence: 99%

First-principles study of oxygen-deficientLaNiO3structures

Malashevich

Ismail‐Beigi

2015

Phys. Rev. B

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“…LaNiO 3 (LNO), possessing a pseudocubic perovskite structure, is a material recently explored in the context of orbital engineering, with the goal of breaking its orbital degeneracy and emulating the single-band structure of the cuprates. [11][12][13] A recent publication on a LaTiO 3 -LaNiO 3 -LaAlO 3 (LTNAO) superlattice demonstrated the successful breaking of this orbital degeneracy by using atomic-layer synthesis to alter its symmetry and filling; an approximately 50% change in the occupation of the Ni d orbitals was reported 14 and verified via X-ray absorption spectroscopy and ab initio theory, confirming the creation of an electronic configuration which approaches a single-band Fermi surface.…”

Section: Introductionmentioning

confidence: 99%

“…The combination of these polar distortions and the symmetry breaking of the superlattice about the LNO results in asymmetric stretching of the NiO 6 oxygen octahedra, leading to a large crystal field splitting and a polarization in the orbital occupations which resembles the arrangement in the high-temperature superconducting cuprates. A previous study 14 infers the charge transfer from the spatially-averaged X-ray absorption spectroscopy (XAS) measurements on the Ti L-edgeand Ni L-edge.…”

Section: Introductionmentioning

confidence: 99%

“…14,15 The principle is based on the transfer of a single electron from the LTO layer (Ti 3+ ) to the LNO layer (Ni 3+ ) due to the mismatch in electronegativity of the two ions. The electron transfer creates a charge imbalance and, hence, a dipole field which leads to large polar distortions with polarization pointing towards the NiO 2 layer of the LNO.…”

Section: Introductionmentioning

confidence: 99%

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Experimental verification of orbital engineering at the atomic scale: Charge transfer and symmetry breaking in nickelate heterostructures

et al. 2017

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Epitaxial strain, layer confinement and inversion symmetry breaking have emerged as powerful new approaches to control the electronic and atomic-scale structural properties in complex metal oxides. Nickelate heterostructures, based on RENiO 3 , where RE is a trivalent rare-earth cation, have been shown to be relevant model systems since the orbital occupancy, degeneracy, and, consequently, the electronic/magnetic properties can be altered as a function of epitaxial strain, layer thickness and superlattice structure. One such recent example is the tri-component LaTiO 3 -LaNiO 3 -LaAlO 3 superlattice, which exhibits charge transfer and orbital polarization as the result of its interfacial dipole electric field. A crucial step towards control of these parameters for future electronic and magnetic device applications is to develop an understanding of both the magnitude and range of the octahedral networks response towards interfacial strain and electric fields.An approach that provides atomic-scale resolution and sensitivity towards the local octahedral distortions and orbital occupancy is therefore required. Here, we employ atomic-resolution imaging coupled with electron spectroscopies and first principles theory to examine the role of interfacial charge transfer and symmetry breaking in a tricomponent nickelate superlattice system. We find that nearly complete charge transfer occurs between the LaTiO 3 and LaNiO 3 layers, resulting in a Ni 2+ valence state. We further demonstrate that this charge transfer is highly localized with a range of about 1 unit cell, within the LaNiO 3 layers. The results presented here provide important feedback to synthesis efforts aimed at stabilizing new electronic phases that are not accessible by conventional bulk or epitaxial film approaches.PACS numbers:

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“…Chemical doping by hydrogen incorporation into nickelate lattices has been shown to modify the ground state properties by inducing a colossal change in the resistivity that can be reversed by removing the dopant species from the lattice 10 . Nickelates have also been proposed to serve as candidate systems for understanding high temperature superconductivity due to the rich physics inherent in d-orbital non-degeneracy [23][24][25] . These interesting observations opens up a possibility of realizing new electrical and magnetic ground states for the electron doped nickelates.…”

Section: Introductionmentioning

confidence: 99%

Sign reversal of magnetoresistance in a perovskite nickelate by electron doping

et al. 2016

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We present low temperature resistivity and magnetotransport measurements conducted on pristine and electron doped SmNiO3 (SNO). The low temperature transport in both pristine and electrondoped SNO shows a Mott variable range hopping with a substantial decrease in localization length of carriers by one order in the case of doped samples. Un-doped SNO films show a negative magnetoresistance (MR) at all temperatures characterized by spin fluctuations with the evolution of a positive cusp at low temperatures. In striking contrast, upon electron doping of the films via hydrogenation, we observe a crossover to a linear non-saturating positive MR∼ 0.2 % at 50 K . The results signify the role of localization phenomena in tuning the magnetotransport response in doped nickelates. Ionic doping is therefore a promising approach to tune magnetotransport in correlated perovskites.

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Orbital Engineering in Symmetry-Breaking Polar Heterostructures

Cited by 153 publications

References 51 publications

First-principles study of oxygen-deficientLaNiO3structures

First-principles study of oxygen-deficientLaNiO3structures

Experimental verification of orbital engineering at the atomic scale: Charge transfer and symmetry breaking in nickelate heterostructures

Sign reversal of magnetoresistance in a perovskite nickelate by electron doping

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