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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.
The electronic correlations in graphene standing on SrTiO₃ and platinum substrates
Jinwoong Hwang,Hyejin Ryu,Hwihyeon Hwang,Min-Jeong Kim,Ji-Eun Lee,Qin Zhou,Debin Wang,Ankit S. Disa,Jonathan Denlinger,Yuegang Zhang,Alessandra Lanzara,Sung-Kwan Mo,Choongyu Hwang 한국진공학회 2018 한국진공학회 학술발표회초록집 Vol.2018 No.2
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>
Temperature-Dependent Electron–Electron Interaction in Graphene on SrTiO<sub>3</sub>
Ryu, Hyejin,Hwang, Jinwoong,Wang, Debin,Disa, Ankit S.,Denlinger, Jonathan,Zhang, Yuegang,Mo, Sung-Kwan,Hwang, Choongyu,Lanzara, Alessandra American Chemical Society 2017 NANO LETTERS Vol.17 No.10
<P>The electron band structure of graphene on SrTiO3 substrate has been investigated as a function of temperature. The high-resolution angle-resolved photoemission study reveals that the spectral width at Fermi energy and the Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a BN substrate. Near the charge neutrality, the energy-momentum dispersion of graphene exhibits a strong deviation from the well-known linearity, which is magnified as temperature decreases. Such modification resembles the characteristics of enhanced electron electron interaction. Our results not only suggest that SrTiO3 can be a plausible candidate as a substrate material for applications in graphene-based electronics but also provide a possible route toward the realization of a new type of strongly correlated electron phases in the prototypical two-dimensional system via the manipulation of temperature and a proper choice of dielectric substrates.</P>
황춘규,강민희,Hwang, Choongyu,Kang, Minhee 한국진공학회 2018 진공 이야기 Vol.5 No.2
The research field of graphene has been rapidly expanded ever since its first experimental realization of Dirac fermions in 2005, due to the fundamental importance in physics as a new paradigm for relativistic condensed matter physics as well as a potential building block for next generation device applications. Most of the intriguing physics observed so far in graphene can be traced to its peculiar electron band structure, which is in analogy with relativistic Dirac fermions. This article reviews recent progress in graphene research that has been done using angle-resolved photoemission technique, the most direct probing tool of the electron band structure. In particular, we discuss a few examples of novel properties so far explored ranging from the basic electron band structure to complicated many-body interactions.