Effect of charge doping on the electronic structure, orbital polarization, and structural distortion in nickelate superlattice

Kim, Heung Sik; Han, Myung Joon

doi:10.1103/physrevb.91.235102

Cited by 11 publications

(5 citation statements)

References 49 publications

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“…From the image the out-of-plane lattice constant of the LaNiO 3 unit cell is measured to be 3.94 Å, 4 ± 0.5% larger than the in-plane lattice constant. This may represent a volume expansion, which has been attributed previously to oxygen vacancies 19,20 , although NiO 6 octahedral rotations are also known to affect bond angles and lengths in LaNiO 3 thin films 21 . X-ray diffraction reciprocal space map of a 50-u.c.-thick film shows a fully strained film, suggesting that all the LaNiO 3 films presented in the work are fully compressively strained to the LaAlO 3 substrate.…”

Section: Resultsmentioning

confidence: 72%

Nature of the metal-insulator transition in few-unit-cell-thick LaNiO3 films

et al. 2018

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The nature of the metal-insulator transition in thin films and superlattices of LaNiO3 only a few unit cells in thickness remains elusive despite tremendous effort. Quantum confinement and epitaxial strain have been evoked as the mechanisms, although other factors such as growth-induced disorder, cation non-stoichiometry, oxygen vacancies, and substrate–film interface quality may also affect the observable properties of ultrathin films. Here we report results obtained for near-ideal LaNiO3 films with different thicknesses and terminations grown by atomic layer-by-layer laser molecular beam epitaxy on LaAlO3 substrates. We find that the room-temperature metallic behavior persists until the film thickness is reduced to an unprecedentedly small 1.5 unit cells (NiO2 termination). Electronic structure measurements using X-ray absorption spectroscopy and first-principles calculation suggest that oxygen vacancies existing in the films also contribute to the metal-insulator transition.

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Section: Resultsmentioning

confidence: 72%

Nature of the metal-insulator transition in few-unit-cell-thick LaNiO3 films

et al. 2018

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“…43 Static correlation effects were considered within DFT+U 44 U = 4 and J = 0.7 eV for Ni 3d, in line with previous work by us and others. 15,16,27,40,45,46 In order to take octahedral tilts fully into account, 40-atom √ 2a × √ 2a × c supercells were used to model the (LNO) 3 /(LAO) 1 (001) SLs. Epitaxial strain is considered by varying the in-plane lattice parameter a from 3.65 to 3.95 Å.…”

Section: Methodsmentioning

confidence: 99%

Inducing n - and p -Type Thermoelectricity in Oxide Superlattices by Strain Tuning of Orbital-Selective Transport Resonances

Geisler

2019

Phys. Rev. Applied

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By combining first-principles simulations including an on-site Coulomb repulsion term and Boltzmann theory, we demonstrate how the interplay of quantum confinement and epitaxial strain allows to selectively design nand p-type thermoelectric response in (LaNiO3)3/(LaAlO3)1(001) superlattices. In particular, varying strain from −4.9 to +2.9 % tunes the Ni orbital polarization at the interfaces from −6 to +3 %. This is caused by an electron redistribution among Ni 3d x 2 −y 2 -and 3d z 2 -derived quantum well states which respond differently to strain. Owing to this charge transfer, the position of emerging cross-plane transport resonances can be tuned relative to the Fermi energy. Already for moderate values of 1.5 and 2.8 % compressive strain, the cross-plane Seebeck coefficient reaches ∼ −60 and +100 µV/K around room temperature, respectively. This provides a novel mechanism to tailor thermoelectric materials. Finally, we explore the robustness of the proposed concept with respect to oxygen vacancy formation. arXiv:1812.00503v2 [cond-mat.mtrl-sci]

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“…48 Static correlation effects were considered within the DFT+U formalism 49 using U = 4 and J = 0.7 eV for Ni 3d, which is in line with previous work by us and others. 24,31,[50][51][52] In order to take octahedral tilts fully into account, we have modeled the (LNO) n /(LAO) n (001) SLs (n = 1, 3; denoted by 1/1 and 3/3 in the following) by using √ 2a × √ 2a × 2c (6c) supercells, rotated by 45 • around the (pseudo-)cubic c axis, that contain 20 (60) atoms in total. We have considered the effect of epitaxial strain by setting the in-plane lattice parameter to a LAO = 3.79 Å, a STO = 3.905 Å, or a DSO = 3.94 Å (DyScO 3 ).…”

Section: Methodsmentioning

confidence: 99%

Confinement- and strain-induced enhancement of thermoelectric properties in LaNiO3/LaAlO3(001) superlattices

Geisler

2018

Phys. Rev. Materials

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By combining ab initio simulations including an on-site Coulomb repulsion term and Boltzmann theory, we explore the thermoelectric properties of (LaNiO3)n/(LaAlO3)n(001) superlattices (n = 1, 3) and identify a strong dependence on confinement, spacer thickness, and epitaxial strain. While the system with n = 3 shows modest values of the Seebeck coefficient and power factor, the simultaneous reduction of the LaNiO3 region and the LaAlO3 spacer thickness to single layers results in a strong enhancement, in particular of the in-plane values. This effect can be further tuned by using epitaxial strain as control parameter: Under tensile strain corresponding to the lateral lattice constant of SrTiO3 we predict in-and cross-plane Seebeck coefficients of ±600 µV/K and an in-plane power factor of 11 µW/K 2 cm for an estimated relaxation time of τ = 4 fs around room temperature. These values are comparable to some of the best performing oxide systems such as Ladoped SrTiO3 or layered cobaltates and are associated with the opening of a small gap (0.29 eV) induced by the concomitant effect of octahedral tilting and Ni-site disproportionation. This establishes oxide superlattices at the verge of a metal-to-insulator transition driven by confinement and strain as promising candidates for thermoelectric materials.

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Effect of charge doping on the electronic structure, orbital polarization, and structural distortion in nickelate superlattice

Cited by 11 publications

References 49 publications

Nature of the metal-insulator transition in few-unit-cell-thick LaNiO3 films

Nature of the metal-insulator transition in few-unit-cell-thick LaNiO3 films

Inducing n - and p -Type Thermoelectricity in Oxide Superlattices by Strain Tuning of Orbital-Selective Transport Resonances

Confinement- and strain-induced enhancement of thermoelectric properties in LaNiO3/LaAlO3(001) superlattices

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