Ji Hoon Shim

We address the fundamental question of crossover from the localized to the itinerant state of a paradigmatic heavy fermion material: CeIrIn5. The temperature evolution of the one-electron spectra and the optical conductivity are predicted from first-principles calculation. The buildup of coherence in the form of a dispersive many-body feature is followed in detail, and its effects on the conduction electrons of the material are revealed. We find multiple hybridization gaps and link them to the c

We have investigated electronic structures of a newly discovered antiperovskite superconductor ${\mathrm{MgCNi}}_{3}$ and related compounds ${\mathrm{MgBNi}}_{3}$ and ${\mathrm{MgNNi}}_{3}.$ In ${\mathrm{MgCNi}}_{3},$ a peak of very narrow and high density of states is located just below the Fermi level, which corresponds to the ${\ensuremath{\pi}}^{*}$ antibonding state of Ni $3d$ and C $2p$ but with the predominant Ni $3d$ character. The prominent nesting feature is observed in the $\ensuremat

We demonstrated the synthesis of a conductive two-dimensional metal-organic framework (MOF) thin film by single-step all-vapor-phase chemical vapor deposition (CVD). The synthesized large-area thin film of Cu₃(C₆O₆)₂ has an edge-on-orientation with high crystallinity. Cu₃(C₆O₆)₂ thin film-based microdevices were fabricated by e-beam lithography and had an electrical conductivity of 92.95 S/cm. Synthesis of co

Finding alternatives for Bi2Te3, the only thermoelectric material for near-room-temperature (RT) applications, is of great importance in thermoelectrics. Here, we report a very promising near-RT thermoelectric figure of merit (ZTmax = 0.9 at 390 K, ZTave = 0.68 between RT and 390 K) for Cu-excess α-Cu2+xSe, comprising low-cost, abundant, and nontoxic elements. Although α-Cu2+xSe has a propensity to form a large number of Cu vacancies to stabilize its structure by diminishing Cu–Cu interactions,

The temperature-dependent evolution of the Kondo lattice is a long-standing topic of theoretical and experimental investigation and yet it lacks a truly microscopic description of the relation of the basic f-c hybridization processes to the fundamental temperature scales of Kondo screening and Fermi-liquid lattice coherence. Here, the temperature dependence of f-c hybridized band dispersions and Fermi-energy f spectral weight in the Kondo lattice system CeCoIn₅ is investigated using f

The Dirac fermions of Sb square net in AEMnSb(2) (AE = Sr, Ba) are investigated by using first-principles calculation. BaMnSb2 contains Sb square net layers with a coincident stacking of Ba atoms, exhibiting Dirac fermion behavior. On the other hand, SrMnSb2 has a staggered stacking of Sr atoms with distorted zig-zag chains of Sb atoms. Application of hydrostatic pressure on the latter induces a structural change from a staggered to a coincident arrangement of AE ions accompanying a transition f

In this article we report point defect-assisted doping mechanism and related thermoelectric transport properties in Pb-doped BiCuOTe compounds.

Magnetic anisotropy energy (MAE) is one of the most important properties in two-dimensional magnetism since the magnetization in two dimension is vulnerable to the spin rotational fluctuations. Using density functional theory calculation, we show that perpendicular electric field dramatically enhances the in-plane and out-of-plane magnetic anisotropies in Fe₃GeTe₂ and Fe₄GeTe₂ monolayers, respectively, allowing the change of easy axis in both systems.

We have investigated the electronic structures of antiperovskite ${\mathrm{GaCMn}}_{3}$ and related Mn compounds ${\mathrm{SnCMn}}_{3},$ ${\mathrm{ZnCMn}}_{3},$ and ${\mathrm{ZnNMn}}_{3}.$ In the paramagnetic state of ${\mathrm{GaCMn}}_{3},$ the Fermi surface nesting feature along the $\ensuremath{\Gamma}R$ direction is observed, which induces the antiferromagnetic (AFM) spin ordering with the nesting vector $\mathbf{Q}\ensuremath{\sim}\ensuremath{\Gamma}R.$ Calculated susceptibilities confirm t

Electronic structures of RTe2 (R=La,Ce) have been investigated by using the local spin density approximation (LSDA) and the LSDA + U (U: on-site Coulomb interaction) band methods. Both LaTe2 and CeTe2 show the very similar Fermi surface nesting features along the [100] direction, which drive the charge-density wave (CDW) instability in the Te(1) sheets. The contribution near E(F) from Ce 4f states is negligible in agreement with the measured ARPES spectra. In the semimetallic CDW-distorted RTe2,