Optical spectroscopy and the nature of the insulating state of rare-earth nickelates

Ruppen, J.; Teyssier, J.; Peil, Oleg E.; Catalano, Sara; Gibert, Marta; Mravlje, Jernej; Triscone, J.‐M.; Georges, Antoine; Marel, D. van der

doi:10.1103/physrevb.92.155145

Cited by 47 publications

(53 citation statements)

References 36 publications

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“…They are also compatible with the model of Mizokawa et al 49 as well as with recent dynamical mean field theory studies and exact Hartree-Fock calculations, 31,32,[50][51][52][53] proposing a ligand-hole structure in rare-earth nickelates. Indeed, our Wannier analysis indicates that we have a 3d 8 electronic configuration for the Ni L cations.…”

Section: Disproportionation Signaturessupporting

confidence: 69%

Complete phase diagram of rare-earth nickelates from first-principles

et al. 2017

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The structural, electronic and magnetic properties of AMO 3 perovskite oxides, where M is a 3d transition metal, are highly sensitive to the geometry of the bonds between the metal-d and oxygen-p ions (through octahedra rotations and distortions) and to their level of covalence. This is particularly true in rare-earth nickelates RNiO 3 that display a metal-insulator transition with complex spin orders tunable by the rare-earth size, and are on the border line between dominantly ionic (lighter elements) and covalent characters (heavier elements). Accordingly, computing their ground state is challenging and a complete theoretical description of their rich phase diagram is still missing. Here, using first-principles simulations, we successfully describe the electronic and magnetic experimental ground state of nickelates. We show that the insulating phase is characterized by a split of the electronic states of the two Ni sites (i.e., resembling low-spin 4+ and high-spin 2+) with a concomitant shift of the oxygen-2p orbitals toward the depleted Ni cations. Therefore, from the point of view of the charge, the two Ni sites appear nearly identical whereas they are in fact distinct. Performing such calculations for several nickelates, we built a theoretical phase diagram that reproduces all their key features, namely a systematic dependence of the metal-insulator transition with the rare-earth size and the crossover between a second to first order transition for R = Pr and Nd. Finally, our results hint at strategies to control the electronic and magnetic phases of perovskite oxides by fine tuning of the level of covalence.npj Quantum Materials (2017) 2:21 ; doi:10.1038/s41535-017-0024-9 INTRODUCTIONTransition metal oxides with an AMO 3 perovskite structure have attracted widespread interest over the last decades, both from academic and application points of view. This can be ascribed to their wide range of functionalities that originates from the interplay between lattice, electronic, and magnetic degrees of freedom.1 Among all perovskites, rare-earth nickelates R 3+ Ni 3+ O 3 (R = Lu-La, Y) might be considered as a prototypical case because they posses almost all possible degrees of freedom present in these materials. Nickelates were intensively studied during the nineties 2, 3 and have regained interest in the last few years due to their great potential for engineering novel electronic and magnetic states.

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Section: Disproportionation Signaturessupporting

confidence: 69%

Complete phase diagram of rare-earth nickelates from first-principles

et al. 2017

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“…Furthermore, the recent DMFT calculations of bulk SNO at low temperature enable us to identify the dominant features of the optical conductivity. Indeed, Ruppen et al 39. demonstrated the peak B (1.4 eV) is due to the optical transition across the Peierls pseudogap, while the peak A’ corresponds to the transition across the insulating gap.…”

Section: Resultsmentioning

confidence: 99%

“…demonstrated the peak B (1.4 eV) is due to the optical transition across the Peierls pseudogap, while the peak A’ corresponds to the transition across the insulating gap. The presence of these peaks results from the combined effect of bond disproportionation and Mott physics associated with half of the disproportionated sites39.…”

Section: Resultsmentioning

confidence: 99%

Metal-Insulator Transition of strained SmNiO3 Thin Films: Structural, Electrical and Optical Properties

Torriss

Margot

Chaker

2017

Sci Rep

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Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. The Mott metal-insulator (MI) transition of the thin films is sensitive to epitaxial strain and strain relaxation. Once the strain changes from compressive to tensile, the transition temperature of the SmNiO3 samples shifts to slightly higher values. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation. Actually, compressive strain broadens the bandwidth. In contrast, tensile strain causes the effective number of free carriers to reduce which is consistent with the d-band narrowing.

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“…3 to that observed in the rare-earth nickelates (RNiO 3 with R=Sm, Eu, Y, or Lu)[58][59][60][61][62]. In fact, the latter exhibit a site-selective Mott transition, characterized by a two-sublattice symmetry breaking, with formation of site-selective local moments with localized Ni3d magnetic moments and Ni-d-O-p singlet nonmagnetic states.…”

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confidence: 86%

Charge disproportionation and site-selective local magnetic moments in the post-perovskite-type Fe2O3 under ultra-high pressures

2019

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The archetypal 3d Mott insulator hematite, Fe 2 O 3 , is one of the basic oxide components playing an important role in mineralogy of Earth's lower mantle. Its high pressuretemperature behavior, such as the electronic properties, equation of state, and phase stability is of fundamental importance for understanding the properties and evolution of the Earth's interior. Here, we study the electronic structure, magnetic state, and lattice stability of Fe 2 O 3 at ultra-high pressures using the density functional plus dynamical mean-field theory (DFT+DMFT) approach. In the vicinity of a Mott transition, Fe 2 O 3 is found to exhibit a series of complex electronic, magnetic, and structural transformations. In particular, it makes a phase transition to a metal with a post-perovskite crystal structure and site-selective local moments upon compression above 75 GPa. We show that the site-selective phase transition is accompanied by a charge disproportionation of Fe ions, with Fe 3±δ and δ ∼ 0.05-0.09, implying a complex interplay between electronic correlations and the lattice. Our results suggest that site-selective local moments in Fe 2 O 3 persist up to ultra-high pressures of ∼200-250 GPa, i.e., sufficiently above the core-mantle boundary. The latter can have important consequences for understanding of the velocity and density anomalies in the Earth's lower mantle.

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Optical spectroscopy and the nature of the insulating state of rare-earth nickelates

Cited by 47 publications

References 36 publications

Complete phase diagram of rare-earth nickelates from first-principles

Complete phase diagram of rare-earth nickelates from first-principles

Metal-Insulator Transition of strained SmNiO3 Thin Films: Structural, Electrical and Optical Properties

Charge disproportionation and site-selective local magnetic moments in the post-perovskite-type Fe2O3 under ultra-high pressures

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