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 2021학년도 1학기 콜로퀴움 일정 2021.01.13 29825
공지 <12/8(Thu.) 11:00am>노벨상 소개 강연 - 2016년 노벨 물리학상: 위상 응집 물리의 탄생 2016.11.28 638875
441 <Oct.20(Tue) 16:00> Electromagnetic Response and Thermomagnetic Instabilities in Three-Dimensional Nanostructured Superconductors file 2015.10.15 43934
440 <Oct.15(Thu) 16:30> Single-Molecule Approach to Homology Search & Strand Exchange in Homologous Recombination 2015.10.12 42542
439 <Oct. 14(Wed.) 4:30 PM> 국방과학기술과 물리학 2015.10.07 52345
438 <Oct. 20(Tue.) 2:00 PM> High-throughput Synthesis of Oxide Thin Films 2015.10.05 45260
437 <Oct. 7(Wed.) 4:30 PM> Observing Ultra High Energy Cosmic Rays with your Smartphone 2015.10.02 46364
436 학술세미나 개최 안내: Local Modes in Vibrational (and Rotational) Spectroscopy file 2015.10.01 42157
» <Sep. 30(Wed.) 4:30 PM>Local electronic structures of stacking grain boundary in bilayer graphene 2015.09.23 53127
434 <Sep. 23(Wed.) 4:30 PM>Grain boundary effect in Metal : A journey of discovery from crystal to thin films without grain boundaries 2015.09.16 47454
433 <Sep. 18(Fri.) 4:00 PM> Special seminar 2015.09.16 43163
432 <Sep. 16(Wed.) 4:30 PM> Watching molecular targets in living bodies: the cutting edge in clinical medicine 2015.09.09 48181
431 <Sep. 9(Wed.) 4:30 PM> Electronic structures of strongly-correlated systems 2015.09.03 50050
430 <8/29(토)> 세미나 개최 안내 2015.09.01 44525
429 2015학년도 2학기 콜로퀴움 일정 2015.08.06 73089
428 <6/9(화)> 세미나 개최 안내 2015.06.09 43525
427 <6/10(수) 오후4:30분> Closing in on the Axion Dark Matter hypothesis 2015.06.03 45962
426 <6/2(화)> 세미나 개최 안내 2015.06.01 44537
425 <6/3(수) 오후4:30분> The Quest for Dark Matter: Discovering Its Nature Underground? 2015.05.28 45519
424 <5/26(화)> 세미나 개최 안내 2015.05.27 43294
423 <5/27(수) 오후4:30분>Controlling phases in epitaxial transition metal oxide thin films 2015.05.21 57631
422 <5/16(토)> 세미나 개최 안내 2015.05.18 123361