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Gapped Nearly Free-Standing Graphene on an SiC(0001) Substrate Induced by Manganese Atoms
Hwang, Jinwoong,Lee, Ji-Eun,Kang, Minhee,Park, Byeong-Gyu,Denlinger, Jonathan,Mo, Sung-Kwan,Hwang, Choongyu The Korean Vacuum Society 2018 Applied Science and Convergence Technology Vol.27 No.5
The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angle-resolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene, that is observed in pristine graphene indicating intrinsic electron-doping by the substrate, completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases by the presence of manganese atoms, approaching the electron band structure calculated using the local density approximation method. The former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition. The latter suggests that its electronic correlations are efficiently screened, suggesting that the dielectric property of the substrate is modified by manganese atoms and indicating that electronic correlations in grpahene can also be tuned by foreign atoms. These results pave the way for promising device application using graphene that is semiconducting and charge neutral.
Emergence of Kondo Resonance in Graphene Intercalated with Cerium
Hwang, Jinwoong,Kim, Kyoo,Ryu, Hyejin,Kim, Jingul,Lee, Ji-Eun,Kim, Sooran,Kang, Minhee,Park, Byeong-Gyu,Lanzara, Alessandra,Chung, Jinwook,Mo, Sung-Kwan,Denlinger, Jonathan,Min, Byung Il,Hwang, Choong American Chemical Society 2018 NANO LETTERS Vol.18 No.6
<P>The interaction between a magnetic impurity, such as cerium (Ce) atom, and surrounding electrons has been one of the core problems in understanding many-body interaction in solid and its relation to magnetism. Kondo effect, the formation of a new resonant ground state with quenched magnetic moment, provides a general framework to describe many-body interaction in the presence of magnetic impurity. In this Letter, a combined study of angle-resolved photoemission (ARPES) and dynamic mean-field theory (DMFT) on Ce-intercalated graphene shows that Ce-induced localized states near Fermi energy, <I>E</I><SUB>F</SUB>, hybridized with the graphene π-band, exhibit gradual increase in spectral weight upon decreasing temperature. The observed temperature dependence follows the expectations from the Kondo picture in the weak coupling limit. Our results provide a novel insight how Kondo physics emerges in the sea of two-dimensional Dirac electrons.</P> [FIG OMISSION]</BR>
Hwang, Minhee,Baek, Hye Jin,Ryu, Kyeong Hwa,Choi, Bo Hwa,Ha, Ji Young,Do, Hyun Jung Korean Society of Magnetic Resonance in Medicine 2019 Investigative Magnetic Resonance Imaging Vol.23 No.2
$M\ddot{o}bius$ syndrome is a rare congenital condition, characterized by abducens and facial nerve palsy, resulting in limitation of lateral gaze movement and facial diplegia. However, to our knowledge, there have been few studies on evaluation of cranial nerves, on MR imaging in $M\ddot{o}bius$ syndrome. Herein, we describe a rare case of $M\ddot{o}bius$ syndrome representing limitation of lateral gaze, and weakness of facial expression, since the neonatal period. In this case, high-resolution MR imaging played a key role in diagnosing $M\ddot{o}bius$ syndrome, by direct visualization of corresponding cranial nerves abnormalities.
Kang, Minhee,Hwang, Jinwoong,Lee, Ji-Eun,Fedorov, Alexei,Hwang, Choongyu Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.467 No.-
<P><B>Abstract</B></P> <P>The interplay between electron-electron interaction and electron-phonon coupling has been one of the key issues in graphene as it can provide information on the origin of enhanced electron-phonon coupling in graphene by foreign atoms. In ytterbium-decorated graphene on SiC substrate, electron-phonon coupling exhibits strong enhancement compared to that of as-grown graphene. Based on angle-resolved photoemission study, the presence of ytterbium is also found to result in the decrease of Fermi velocity, revealing the enhancement of electron-electron interaction within the Fermi liquid theory. Our finding on the concomitant enhancement of electron-electron interaction and electron-phonon coupling suggests a possibility of the interplay between the two representative many-body interactions in graphene decorated with foreign atoms.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ytterbium-decorated graphene shows enhanced electron-phonon (el-ph) coupling. </LI> <LI> Ytterbium also leads to the enhancement of electron-electron (el-el) interaction in graphene. </LI> <LI> The concomitant enhancement indicates an interplay between el-el and el-ph interations. </LI> <LI> This result suggests a plausible route towards the realization of superconducting graphene. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Bio-signal based Emotion Visualization Map System using Smartphone
Minhee Kim,SungTeac Hwang,Dong Keun Kim,Mincheol Whang 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.5
Recently location-based services industry has improved leading to rapid evolution of space-based sentiment visualization applications. While there is ongoing research on sentiment vocabulary based visualization of sentiments, there has been no research on bio signal based sentiment visualization in real time. In this research, using a smartphone, sentiments were classified as arousal, neutral, and relaxation on the basis of the measured pulse rate. An application to visualize these sentiments on map has also been implemented. The application works as follows. First, using a smart phone, pulse rate is measured. Then the bio-signal based sentiments are classified into three classes viz., arousal (pulse rate above 79 bpm), neutral (pulse rate between 61-79 bpm), and relaxation (pulse rate below 61 bpm). Next, the computed sentiment class and the user’s location data (latitude and longitude) measured using GPS were are stored in SQLite DB. Finally, these data values are marked on a map with Google map API. The results of this research indicate a person"s spatial sentiment that can be used as a social indicator.