Korea Advanced Institute of Science and Technology · Materials Science
Professor Myung Joon Han's research lab specializes in theoretical and computational materials science, focusing on strongly correlated electron systems in complex oxides. The lab employs advanced first-principles methods such as density functional theory (DFT), dynamical mean-field theory (DMFT), and LDA+U to investigate electronic structure, magnetism, and electron correlation effects in transition metal oxides, including iron-based superconductors, multiferroics, and oxide heterostructures. A central theme is understanding how electronic properties—such as orbital occupancy, magnetic interactions, and electronic phase transitions—can be controlled through doping, strain, interface engineering, and atomic site disorder. The lab also explores the interplay between electron correlation, charge transfer, and orbital polarization in complex oxide superlattices and heterostructures.
Figures are computed from collected data and may differ slightly.
We report an implementation of the $\mathrm{LDA}+U$ method based on the state-of-the-art linear combination of pseudo-atomic orbital (LCPAO) method, which is suitable for large-scale $\mathrm{O}(N)$ electronic structure calculations based on the density functional theory. By introducing a dual representation of the occupation number matrix instead of the on-site or full representations, the $\mathrm{LDA}+U$ formalism is refined to be consistent with a nonorthogonal LCPAO basis in regard to the s
Using first-principles density functional theory calculations combined with insight from a tight-binding representation, dynamical mean field theory, and linear response theory, we have extensively investigated the electronic structures and magnetic interactions of nine ferropnictides representing three different structural classes. The calculated magnetic interactions are found to be short range, and the nearest (J_{1a}) and next-nearest (J2) exchange constants follow the universal trend of J_{
Dynamical mean-field methods are used to calculate the phase diagram, many-body density of states, relative orbital occupancy, and Fermi-surface shape for a realistic model of LaNiO(3)-based superlattices. The model is derived from density-functional band calculations and includes oxygen orbitals. The combination of the on-site Hunds interaction and charge transfer between the transition metal and the oxygen orbitals is found to reduce the orbital polarization far below the levels predicted eith
To understand newly discovered superconductivity in Fe-based systems, we investigate the electronic structure and magnetic properties of Fe_{1+x}Te using first-principles density functional calculations. While the undoped FeTe has the same Fermi surface nested at (pi,pi) as in Fe arsenides, doping by approximately 0.5 electrons reveals a novel square-type Fermi surface showing a strong (pi,0) nesting and leading to a different magnetic structure. Our result strongly supports the same mechanism o
We report our first-principles calculations on multiferroic $\mathrm{Ga}\mathrm{Fe}{\mathrm{O}}_{3}$. The total energy results for different spin and structural configurations reveal that the ground state of $\mathrm{Ga}\mathrm{Fe}{\mathrm{O}}_{3}$ in its ideal structure is antiferromagnetic but it is likely to have a possible site disorder of Fe and Ga atoms between octahedral Ga sites and Fe sites, which is consistent with previous experimental observations. Examining the exchange interactions
The application of modern layer-by-layer growth techniques to transition-metal oxide materials raises the possibility of creating new classes of materials with rationally designed correlated electron properties. An important step toward this goal is the demonstration that electronic structure can be controlled by atomic composition. In compounds with partially occupied transition-metal $d$ shells, one important aspect of the electronic structure is the relative occupancy of different $d$ orbital
We report our first principles calculation studies of electronic structure and magnetic properties of the ${\mathrm{Mn}}_{n}$ $(n=4,12)$ single-molecule magnet, i.e., $[{\mathrm{Mn}}_{4}{\mathrm{O}}_{3}\mathrm{Cl}{(\mathrm{OAc})}_{3}{(\mathrm{dbm})}_{3}]$ $(\mathrm{dbmH}=\text{dibenzoyl}\text{\ensuremath{-}}\text{methane})$ and $[{\mathrm{Mn}}_{12}{\mathrm{O}}_{12}{({\mathrm{CH}}_{3}\mathrm{COO})}_{16}{({\mathrm{H}}_{2}\mathrm{O})}_{4}]$ molecules. For the calculations, we used the localized pse
Recent experimental findings of two dimensional ferromagnetism in Fe3GeTe2, whose critical temperature can reach room temperature by gating, has attracted great research interest. Here we performed elaborate ab initio studies using density functional theory, dynamical mean-field theory and magnetic force response theory. In contrast to the conventional wisdom, it is unambiguously shown that Fe3GeTe2 is not ferromagnetic but is antiferromagnetic, carrying zero net moment in its stoichiometric pha
First-principles calculations predict that rotating one layer by 180° over the other layer can switch the interlayer magnetic order in bilayer CrI 3 , demonstrating stacking rotation as an effective strategy to manipulate the magnetism in 2D magnets.
To investigate the electronic structure and magnetic properties of manganese oxide clusters, we carried out first-principles electronic structure calculations for small MnO clusters. Among various structural and magnetic configurations of the clusters, the bulklike [111]-antiferromagnetic ordering is found to be favored energetically, while the surface atoms of the clusters exhibit interesting electronic and magnetic characteristics which are different from their bulk ones. The distinct features
Abstract Herein, the synthesis of novel, highly luminescent, and nearly monodisperse zero‐dimensional (0D) cesium lanthanide chloride (Cs 3 LnCl 6 ; Ln = Y, Ce, Gd, Er, Tm, Yb) colloidal nanocrystals (NCs) is reported for the first time. The Cs 3 LnCl 6 NCs are synthesized using a heating‐up method and exhibit highly uniform size and shape. The monoclinic‐phase Cs 3 LnCl 6 NCs contain completely isolated [LnCl 6 ] 3− octahedral units, resulting in 0D ternary metal halide structures. Therefore, t
Density functional band calculations have been performed to study LaNiO${}_{3}$/LaAlO${}_{3}$ superlattices. Motivated by recent experiments reporting the magnetic and metal-insulator phase transition as a function of LaNiO${}_{3}$ layer thickness, we examined the electronic structure, magnetic properties, and orbital occupation depending on the number of LaNiO${}_{3}$ layers. Calculations show that the magnetic phase is stabler than the nonmagnetic for finite and positive $U$ values. The orbita
Spin-polarized bands in pristine and proximity-induced magnetic materials are promising building blocks for future devices. Conceptually new memory, logic, and neuromorphic devices are conceived based on atomically thin magnetic materials and the manipulation of their spin-polarized bands via electrical and optical methods. A critical remaining issue is the direct probe and the optimized use of the magnetic coupling effect in van der Waals heterostructures, which requires further delicate design
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