A5060095235- 2D Materials and Applications
- Physics of Superconductivity and Magnetism
- High-pressure geophysics and materials
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Geological and Geochemical Analysis
- Topological Materials and Phenomena
- Graphene research and applications
- Geomagnetism and Paleomagnetism Studies
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Electronic and Structural Properties of Oxides
- Quantum and electron transport phenomena
- Perovskite Materials and Applications
- Organic and Molecular Conductors Research
- Nuclear Materials and Properties
- Solid-state spectroscopy and crystallography
- Advanced Memory and Neural Computing
- Transition Metal Oxide Nanomaterials
- Superconductivity in MgB2 and Alloys
- Chalcogenide Semiconductor Thin Films
- Intellectual Capital and Performance Analysis
- Magnetic Properties and Synthesis of Ferrites
- Methane Hydrates and Related Phenomena
- Boron and Carbon Nanomaterials Research
Los Alamos National Laboratory
2022-2024
Kyung Hee University
2023-2024
Center for Integrated Nanotechnologies
2023-2024
Center for High Pressure Science and Technology Advanced Research
2020-2023
Korea Institute for Advanced Study
2021-2023
Pohang University of Science and Technology
2015-2022
Center for High Pressure Science & Technology Advanced Research
2022
Korea Research Institute of Standards and Science
2015
A theoretically designed van der Waals ferromagnet Fe 4 GeTe 2 is synthesized and shows the nearly room temperature ferromagnetism.
Two-dimensional stacks of dissimilar hexagonal monolayers exhibit unusual electronic, photonic and photovoltaic responses that arise from substantial interlayer excitations. Interband excitation phenomena in individual monolayer occur states at band edges (valleys) the momentum space; therefore, low-energy can be directed by two-dimensional rotational degree each crystal. However, this rotation-dependent is largely unknown, due to lack control over relative rotations, thereby leading...
Significance The temperature ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>T</mml:mi> </mml:math> )-dependent evolution of the Kondo lattice electronic structure is a long-standing topic theoretical and experimental investigation, still lacking truly microscopic theory that agrees with full characterization. Here multiple characteristic scales interaction localized <mml:mi>f</mml:mi> moments conduction electrons in CeCo <mml:msub> <mml:mrow> <mml:mi...
Abstract Magnetic anisotropy energy (MAE) is one of the most important properties in two-dimensional magnetism since magnetization two dimension vulnerable to spin rotational fluctuations. Using density functional theory calculation, we show that perpendicular electric field dramatically enhances in-plane and out-of-plane magnetic anisotropies Fe 3 GeTe 2 4 monolayers, respectively, allowing change easy axis both systems. The changes MAE under are understood as result charge redistribution...
Magnetism in two-dimensional (2D) materials has attracted considerable attention recently for both fundamental understanding of magnetism and its tunability towards device applications. The isostructural Fe3GeTe2 Fe3GaTe2 are two members the Fe-based van der Waals (vdW) ferromagnet family, but exhibit very different Curie temperatures (TC) 210 360 K, respectively. Here, by using angle-resolved photoemission spectroscopy density functional theory, we systematically compare electronic...
Abstract Non-volatile phase-change memory devices utilize local heating to toggle between crystalline and amorphous states with distinct electrical properties. Expanding on this kind of switching two topologically phases requires controlled non-volatile symmetries. Here, we report the observation reversible stable closely related crystal structures, remarkably electronic in near-room-temperature van der Waals ferromagnet Fe 5− δ GeTe 2 . We show that is enabled by ordering disordering site...
Abstract Two-dimensional van der Waals (vdW) magnetic materials have emerged as possible candidates for future ultrathin spintronic devices, and finding a way to tune their physical properties is desirable wider applications. Owing the sensitivity tunability of variation interatomic separations, this class attractive explore under pressure. Here, we present observation direct indirect band gap crossover an insulator–metal transition in vdW antiferromagnetic insulator CrPS 4 pressure through...
Iron oxide is a key compound to understand the state of deep Earth. It has been believed that previously known oxides such as FeO and Fe2O3 will be dominant at mantle conditions. However, recent observation FeO2 shed another light composition lower (DLM) thus understanding physical properties critical model DLM. Here, we report electronic structure structural by using density functional theory (DFT) dynamic mean field (DMFT). The crystal composed Fe2+ O2 2- dimers, where Fe ions are surround...
Two-dimensional materials represent a major frontier for research into exotic many-body quantum phenomena. In the extreme two-dimensional limit, electron-electron interaction often dominates over other electronic energy scales, leading to strongly correlated effects such as spin liquid and unconventional superconductivity. The dominance is conventionally attributed lack of electron screening in third dimension. Here, we discover an intriguing metal Mott insulator transition 1T-TaSe
Using ab initio approaches for extended Hubbard interactions coupled to phonons, we reveal that the intersite Coulomb interaction plays important roles in determining various distinctive phases of paradigmatic charge-ordered materials Ba_{1-x}K_{x}AO_{3} (A=Bi and Sb). We demonstrated all their salient doping dependent experiment features such as breathing instabilities, anomalous phonon dispersions, transition between charge-density wave superconducting states can be accounted very well if...
Abstract Understanding characteristic energy scales is a fundamentally important issue in the study of strongly correlated systems. In multiband systems, an scale affected not only by effective Coulomb interaction but also Hund’s coupling. Direct observation such has been elusive so far spite extensive studies. Here, we report kink structure low dispersion NiS 2− x Se and its evolution with , using angle resolved photoemission spectroscopy. Dynamical mean field theory calculation combined...
Abstract The discovery of two-dimensional (2D) van der Waals (vdW) materials often provides interesting playgrounds to explore novel phenomena. One the missing components in 2D vdW is intrinsic heavy-fermion systems, which can provide an additional degree freedom study quantum critical point (QCP), unconventional superconductivity, and emergent phenomena heterostructures. Here, we investigate candidates through database experimentally known compounds based on dynamical mean-field theory...
Strong correlation effects caused by Hund's coupling have been actively studied during the past decade. metal, strongly correlated while far from Mott insulating limit, was as a representative example. However, recently it revealed that typical system also exhibits sign of Hund physics investigating kink structure in spectral function ${\mathrm{NiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$. Therefore, to understand half-filled multiorbital near metal-insulator transition, we pressure-induced...
The discovery of ${\mathrm{FeO}}_{2}$ containing more oxygen than hematite $({\mathrm{Fe}}_{2}{\mathrm{O}}_{3})$, which was previously believed to be the most rich iron compound, has important implications for study deep lower mantle compositions. Compared other compounds, there are limited reports on ${\mathrm{FeO}}_{2}$, making studies its physical properties great interest in fundamental condensed matter physics and geoscience. Even oxidation state Fe is subject debate theoretical works...
We investigate the evolution of electronic structure ${\mathrm{NiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ alloys with varying temperature and composition $x$ by using combined approach density-functional theory dynamical mean-field theory. Adopting realistic alloy structures containing S Se dimers, we map their correlation strength on phase diagram observe metal-insulator transition (MIT) at $x=0.5$, which is consistent experimental measurements. The dependence local magnetic susceptibility...
Anomalous transport responses, dictated by the nontrivial band topology, are key for application of topological materials to advanced electronics and spintronics. One promising platform is nodal-line semimetals due their rich topology exotic physical properties. However, signatures have often been masked complexity in crossings or coexisting topologically trivial states. Here we show that, slightly hole-doped SrAs3, single-loop states well-isolated from entirely determine responses. The...
Abstract Monolayer (1L) group VI transition metal dichalcogenides (TMDs) exhibit broken inversion symmetry and strong spin‐orbit coupling, offering promising applications in optoelectronics valleytronics. Despite their direct bandgap, high absorption coefficient, spin‐valley locking K or K’ valleys, the ultra‐short valley lifetime limits room‐temperature applications. In contrast, multilayer TMDs, with more absorptive layers, sacrifice bandgap polarization upon gaining from bilayer...
Magnetism in two-dimensional (2D) materials has attracted considerable attention recently for both fundamental understanding of magnetism and their tunability towards device applications. The isostructural Fe$_3$GeTe$_2$ Fe$_3$GaTe$_2$ are two members the Fe-based van der Waals (vdW) ferromagnet family, but exhibit very different Curie temperatures (T$_C$) 210 K 360 K, respectively. Here, by using angle-resolved photoemission spectroscopy density functional theory, we systematically compare...
In low dimensions, the combined effects of interactions and quantum fluctuations can lead to dramatically new physics distinct from that existing in higher dimensions. Here, we investigate electronic optical properties ${\mathrm{CeIr}}_{3}{\mathrm{B}}_{2}$, a quasione-dimensional (1D) Kondo lattice system, using $ab\phantom{\rule{4pt}{0ex}}initio$ calculations. The Ce atoms hexagonal crystal structure form 1D chains along $c$ axis, with extremely short Ce-Ce distances. quasi-1D nature is...
We study the lattice dynamics of antiferromagnetic transition-metal oxides by using self-consistent Hubbard functionals. calculate ground states with on-site and intersite interactions determined self-consistently within framework density functional theory. The terms fix errors associated electron self-interaction in local semilocal Inclusion addition to produces accurate phonon dispersion oxides. Calculated Born effective charges high-frequency dielectric constants are good agreement...
The ability to reversibly toggle between two distinct states in a non-volatile method is important for information storage applications. Such devices have been realized phase-change materials, which utilizes local heating methods crystalline and an amorphous state with electrical properties. To expand such kind of switching topologically phases requires symmetries. Here we report the observation reversible stable closely-related crystal structures remarkably electronic near room temperature...
Whether or not epitaxially grown superconducting films have the same bulk-like properties is an important concern. We report structure and electronic of Ba(Fe1-x Co x )2As2 using scanning tunneling microscopy spectroscopy (STS). This film showed a different surface structure, [Formula: see text]R45° reconstruction, from those as-cleaved surfaces bulk crystals. The that in bulk, it notable exhibits transport properties. found gap at screened Ba layer STS measurements, charge density wave was...