Seoul National University · Materials Science
Professor Kee Hoon Kim's research lab specializes in the electronic and lattice dynamics of strongly correlated oxides, with a focus on manganites, transparent conducting oxides, and quantum materials. The lab investigates phenomena such as electron-phonon coupling, polaronic transport, metal-insulator transitions, and quantum criticality using advanced spectroscopic and transport techniques. Key research directions include the interplay between magnetism, charge order, and lattice distortions in complex oxides, as well as the development of transparent oxide semiconductors for next-generation optoelectronic and energy applications. The lab also explores quantum critical behavior in heavy fermion systems, particularly in URu2Si2, under extreme conditions of temperature and magnetic field.
Figures are computed from collected data and may differ slightly.
Infrared reflectivity spectra were measured for a polycrystalline ${\mathrm{La}}_{0.7}$${\mathrm{Ca}}_{0.3}$Mn${\mathrm{O}}_{3}$ sample. The internal phonon modes, i.e., the bending and stretching modes, of the Mn${\mathrm{O}}_{6}$ octahedra show significant frequency shifts near the Curie temperature ${T}_{C}$. The frequency shifts of the internal phonon modes were found to have a linear relationship with the excess lattice expansion above ${T}_{C}$, which deviates from a prediction of the Gr\"
We measured thermal conductivity kappa, thermoelectric power S, and electric conductivity sigma of La(5/8-x)Pr(x)Ca(3/8)MnO3, showing an intricate interplay between metallic ferromagnetism (FM) and charge ordering (CO) instability. The change of kappa, S, and sigma with temperature (T) and x agrees well with the effective medium theories for binary metal-insulator mixtures. This agreement clearly demonstrates that with the variation of T as well as x, the relative volumes of FM and CO phases dra
Temperature dependent optical conductivity spectra of a ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ (LCMO) sample were measured. In the metallic regime at very low temperatures, they clearly showed two types of absorption features, i.e., a sharp Drude peak and a broad midinfrared absorption band, which could be explained as coherent and incoherent bands of a large lattice polaron. Electrodynamic analyses suggest that the elementary excitation in LCMO should be in a strong coupling
Transparent conducting oxides (TCOs) and transparent oxide semiconductors (TOSs) have become necessary materials for a variety of applications in the information and energy technologies, ranging from transparent electrodes to active electronics components. Perovskite barium stannate (BaSnO 3 ), a new TCO or TOS system, is a potential platform for realizing optoelectronic devices and observing novel electronic quantum states due to its high electron mobility, excellent thermal stability, high tra
A comprehensive transport study, as a function of temperature and continuous magnetic fields of up to 45 T, reveals that URu2Si2 possesses all the essential hallmarks of quantum criticality at fields around 37+/-1 T. The formation of multiple phases at low temperatures at and around the quantum critical point suggests the existence of competing order parameters.
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