logo

korean english

게시판

Home > 게시판 > 세미나

아래와 같이 콜로퀴움을 개최하오니 많이 참석해 주시기 바랍니다.

4시 20분부터 제1과학관 31214 e+강의실에서 다과를 준비하오니 많은 참석 부탁드립니다.



아 래


Title: Local electronic structures of stacking grain boundary in bilayer graphene

 
Speaker: Prof. Gunn Kim (Department of Physics & Astronomy, Sejong University)


Date & Time: Sep. 30 (Wed.) 2015, 4:30 PM


Place: Natural Science 1,  Room No. 31214


Abstract: Gap opening is possible in bilayer graphene (BLG), thus making it a very promising material that overcomes graphene’s key limitation while retaining many of its interesting properties. For example, massive Dirac fermions in BLG exhibit a band gap tunable by applying a transverse electric field (E field); this has been demonstrated by optical and electrical transport measurements using dual-gated devices. However, these measurements leave a couple of unsolved problems: (i) the origin of unexpectedly small transport gaps that are 2 orders of magnitude smaller than optical gaps and (ii) the origin of anomalous low-temperature (< 2 K) transport behaviors dominated by hopping between localized midgap states, presumably induced from disorder or defects.


Recent experiments have revealed complex configurations in BLG, including various stacking domains induced by rotational faults and soliton formation. While AB stacking is energetically most favorable, the non-ABstacking region can be stabilized by a minute twist and the stacking boundary. The local stacking configuration is strongly coupled to its electronic structure and its response to an external E field. Therefore, it is critically important, fundamentally and practically, to understand the observed complex stacking configurations and their impact on the overall electronic properties.

In this talk, I will present gap-opening properties of BLG near the high-symmetry stackings (AA, AA’, and AB), under an applied E field. We establish a phase diagram for the stacking-dependent gap openings and further identify grain boundaries containing non-AB stackings as a source for high-density midgap states even under a strong E field. Our findings offer insight to understanding the intrinsic transport properties of BLG.

Within density functional theory, our calculations adopt the Perdew-Burke-Ernzerhof version of the exchange-correlation functional and the projector augmented wave method for ionic potentials. We obtain interlayer distances between 3.25 (AB) and 3.45 A (AA) with van der Waals correction. To ensure an accurate band gap, the 2D DFT band structure near the K point is interpolated by using maximally localized Wannier functions. Effective Hamiltonians are constructed with the obtained hopping parameters truncated to the first-nearest-interlayer hopping.


번호 제목 날짜 조회 수
공지 <12/8(Thu.) 11:00am>노벨상 소개 강연 - 2016년 노벨 물리학상: 위상 응집 물리의 탄생 2016.11.28 1091368
176 <9/21> Electronic phase transition in low dimensional SrTiO3/(Sr1-x,Lax)TiO3 oxide superlattices 2011.09.09 84941
175 <May.2(Wed.) 4:30 PM> Machine learning and statistical physics 2018.04.23 85079
174 <4/6> Introduction to Superconducting Quantum Electronics 2007.04.03 85182
173 <5/4> Kondo effect in nanoscopic devices 2011.04.28 85184
172 <April. 5 (Wed.) 4:30 PM>Majorana quasiparticles emergent in Kitaev quantum magnets 2017.03.31 85197
171 <4/14> Neutron Star 2006.04.10 85249
170 <Dec. 7(Wed.) 4:30 PM>Mechanotransduction of cells in vitro(세포기능의 역학적 조절) 2016.11.30 85290
169 <5/25> 나노켈빈 원자 기체의 보즈-아인슈타인 응집 2011.05.18 85561
168 <5/2> Electrical Instability in Nanoscale Channel Devices: Top-down & Bottom-up Approaches 2012.04.19 85679
167 <3/23> 동서양의 세계관과 풍경화 2011.03.17 85908
166 2012학년도 1학기 콜로퀴움 일정 안내 [5] 2012.02.29 86195
165 <11/7> Two- and three- body problems in classic and quantum mechanics 2012.10.29 86310
164 <3/30> Supersolidity in Helium 2011.03.25 86456
163 <9/5> Dark Matter and Dark Energy in Cosmology 2008.09.01 86576
162 <3/27> Proximity effects and low dimensional superconductivity of Pb nano-islands  2013.03.21 86807
161 essay 작성요령 2008.03.18 86860
160 <4/4> Cooking up elements in the universe: Nuclear astrophysics with exotic ion beams 2012.03.29 87080
159 <11/12(수)> Photovoltaic effect and polarization-modulated conduction in ferroelectrics 2014.11.05 87843
158 <5/8>Recent trend of thin film battery 2009.05.06 88072
157 <5/19> Higgs 입자 사냥 2006.05.17 88717