Kee Hoon Kim
서울대학교 물리천문학부 · 재료과학
김기훈 교수의 연구실은 페로브스카이트 망간산화물과 같은 강한 전자-격자 상호작용을 보이는 물질을 중심으로, 전자상태와 격자의 상호작용이 물질의 전기적, 자기적 성질에 미치는 영향을 연구합니다. 특히, 전자-격자 결합, 폴라론 형성, 양자临계점 현상, 그리고 투명 산화물 반도체에서의 전자 구조 제어를 핵심 연구 주제로 삼고 있습니다. 다양한 실험 기법(적외선 반사율, 열전도도, 광학 전도도, 전기적 성질 측정 등)을 통해 복잡한 상전이와 전도성 메커니즘을 규명하고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
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.
