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Robust quantum oscillation of Dirac fermions in a single-defect resonant transistor
Heejun Yang 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
While the massless Dirac fermions produce large energy gaps between Landau levels (LLs), exploiting the quantum Hall effect at room temperature requires large magnetic fields to overcome the energy level broadening by charge inhomogeneities in the device. In this talk, I will demonstrate the robust quantum oscillations of Dirac fermions in a single-defect resonant transistor, which is based on local tunneling between lattice-orientation- aligned graphene layers. A point defect in the h-BN, selected by the orientation-tuned graphene layers, probes local LLs in its proximity at room temperature and low magnetic field (2 Tesla) by minimizing the energy broadening of the LLs by charge inhomogeneity.
Quantum Interference Channeling at Graphene Edges
Yang, Heejun,Mayne, Andrew J.,Boucherit, Mohamed,Comtet, Geneviè,ve,Dujardin, Gé,rald,Kuk, Young American Chemical Society 2010 NANO LETTERS Vol.10 No.3
<P>Electron scattering at graphene edges is expected to make a crucial contribution to the electron transport in graphene nanodevices by producing quantum interferences. Atomic-scale scanning tunneling microscopy (STM) topographies of different edge structures of monolayer graphene show that the localization of the electronic density of states along the C−C bonds, a property unique to monolayer graphene, results in quantum interference patterns along the graphene carbon bond network, whose shapes depend only on the edge structure and not on the electron energy.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-3/nl9038778/production/images/medium/nl-2009-038778_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038778'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038778'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038778'>ACS Electronic Supporting Info</A></P>
Structural and quantum-state phase transition in van der Waals layered materials
Yang, Heejun,Kim, Sung Wng,Chhowalla, Manish,Lee, Young Hee Nature Publishing Group, a division of Macmillan P 2017 Nature physics Vol.13 No.10
<P>Van der Waals layered transition metal dichalcogenides can exist in many different atomic and electronic phases. Such diverse polymorphisms not only provide a route for investigating novel topological states, such as quantum spin Hall insulators, superconductors and Weyl semimetals, but may also have applications in fields ranging from electronic and optical/ quantum devices to electrochemical catalysis. And the methods for triggering robust phase transitions between polymorphs are evolving and diversifying-several growth processes, high-pressure/strain methods, and optical, electronic and chemical treatments have been developed. Here, we discuss recent progress on phase transitions and the related physics in layered materials, and demonstrate unique features compared with conventional solid-state materials.</P>
Remediation of heavy metal-contaminated soils using eco-friendly nano-scale chelators
Lim, Heejun,Park, Sungyoon,Yang, Jun Won,Cho, Wooyoun,Lim, Yejee,Park, Young Goo,Kwon, Dohyeong,Kim, Han S. Techno-Press 2018 Membrane water treatment Vol.9 No.3
Soil washing is one of the most frequently used remediation technologies for heavy metal-contaminated soils. Inorganic and organic acids and chelating agents that can enhance the removal of heavy metals from contaminated soils have been employed as soil washing agents. However, the toxicity, low removal efficiency and high cost of these chemicals limit their use. Given that humic substance (HS) can effectively chelate heavy metals, the development of an eco-friendly, performance-efficient and cost-effective soil washing agent using a nano-scale chelator composed of HS was examined in this study. Copper (Cu) and lead (Pb) were selected as target heavy metals. In soil washing experiments, HS concentration, pH, soil:washing solution ratio and extraction time were evaluated with regard to washing efficiency and the chelation effect. The highest removal rates by soil washing (69% for Cu and 56% for Pb) were achieved at an HS concentration of 1,000 mg/L and soil:washing solution ratio of 1:25. Washing with HS was found to be effective when the pH value was higher than 8, which can be attributed to the increased chelation effect between HS and heavy metals at the high pH range. In contrast, the washing efficiency decreased markedly in the low pH range due to HS precipitation. The chelation capacities for Cu and Pb in the aqueous phase were determined to be 0.547mmol-Cu/g-HS and 0.192mmol-Pb/g-HS, respectively.