Publications by authors named "Leonid Pourovskii"
Clarifying the underlying mechanisms that govern ordering transitions in condensed matter systems is crucial for comprehending emergent properties and phenomena. While transitions are often classified as electronically driven or lattice-driven, we present a departure from this conventional picture in the case of the double perovskite BaMgReO. Leveraging resonant and non-resonant elastic x-ray scattering techniques, we unveil the simultaneous ordering of structural distortions and charge quadrupoles at a critical temperature of T ~ 33 K.
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- Polarons, resulting from strong electron-phonon interactions, and spin-orbit coupling, which occurs in materials with heavy atoms, both significantly affect how charge and spin behave in certain materials, especially in transition metal oxides.
- The study introduces a new compound, BaNaCaOsO, where these two effects, usually considered separate, are found to interact and create "spin-orbital bipolarons."
- As more electrons are added to BaNaCaOsO, it maintains its insulating properties with a stable Mott gap, preventing it from transitioning to a metallic state, even at high levels of electron doping.
Article Synopsis
- Terbium metal, when in its ferromagnetic state, exhibits a unique low-symmetry orthorhombic structure, contrasting with the typical high-symmetry structures seen in most metals.
- This structure, which shares similarities with certain actinide metals like uranium and plutonium, features specific configurations of Tb atoms creating layers that stack in a particular orientation.
- The stabilization of this unusual structure is explained by magneto-elastic forces linked to the arrangement of electron moments, which is important for understanding terbium's magnetic properties and electronic behavior.
Article Synopsis
- The study addresses conflicting views on the quantum magnetic state of spin-orbit coupled d² double perovskites, focusing on whether their ground state features Janh-Teller-distorted quadrupoles or octupolar order.
- Through direct calculations and inelastic neutron scattering for the d² double perovskite series Ba₂MOsO₆ (with M being Ca, Mg, Zn), the researchers uncover that the ground state consists of ferro-ordered octupoles connected via superexchange interactions.
- Findings indicate the calculated ordering temperature aligns with observed trends in experiments, and slight changes in the cubic structure can significantly alter the magnetic excitations' characteristics.
Hidden order and multipolar exchange striction in a correlated -electron system.
Proc Natl Acad Sci U S A
April 2021
The nature of order in low-temperature phases of some materials is not directly seen by experiment. Such "hidden orders" (HOs) may inspire decades of research to identify the mechanism underlying those exotic states of matter. In insulators, HO phases originate in degenerate many-electron states on localized f or d shells that may harbor high-rank multipole moments.
View Article and Find Full Text PDFElectronic correlations in dense iron: from moderate pressure to Earth's core conditions.
J Phys Condens Matter
September 2019
We discuss the role of dynamical many-electron effects in the physics of iron and iron-rich solid alloys under applied pressure on the basis of recent ab initio studies employing the dynamical mean-field theory (DMFT). We review in detail two particularly interesting regimes: first, a moderate pressure range up to 60 GPa and, second, the ultra-high pressure of about 360 GPa expected inside the solid inner core of Earth. Electronic correlations in iron under the moderate pressure of several tens GPa are discussed in the first section.
View Article and Find Full Text PDFA quantum critical point arises at a continuous transformation between distinct phases of matter at zero temperature. Studies in antiferromagnetic heavy-fermion materials have revealed that quantum criticality has several classes, with an unconventional type that involves a critical destruction of the Kondo entanglement. To understand such varieties, it is important to extend the materials basis beyond the usual setting of intermetallic compounds.
View Article and Find Full Text PDFRare-earth vs. heavy metal pigments and their colors from first principles.
Proc Natl Acad Sci U S A
January 2013
Article Synopsis
- Many inorganic pigments, often containing harmful heavy metals, are being replaced with nontoxic alternatives derived from rare-earth elements, but understanding their color properties is complex.
- This study focuses on computing the colors of cerium fluorosulfide and mercury sulfide pigments using advanced computational techniques that consider optical absorption and how factors like film thickness and pigment concentration impact coloration.
- The findings reveal that while mercury sulfide meets performance criteria due to its wide band transitions, cerium fluorosulfide achieves its bright red color through a unique combination of quasi-2D states and localized properties, showcasing the potential of computational methods in designing materials with specific optical characteristics.
Article Synopsis
- The study investigates the effects of strong correlations in rare-earth pnictides, focusing on localized 4f states and their impact on valence electron states.
- Using erbium arsenide as a case study, the researchers apply dynamical mean-field theory to analyze the 4f shell's atomic multiplet structure and its interaction with electronic Fermi surfaces.
- The findings help clarify the long-standing issue of magnetization saturation in magnetic fields and provide quantitative alignment with experimental data on Shubnikov-de Haas frequencies related to Fermi surfaces.