고체전자구조계산연구실(김영국 교수님)에서 Virginia Polytechnic Institute and State University의 박경화 교수님을 초청하여 아래와 같이 세미나를 개최합니다.

학과 구성원 여러분의 많은 참석을 부탁드립니다.

○ 일시: 2017년 7월 20일(목) 오후 2:00

○ 장소: 물리학과 세미나실 (제1과학관 3층 31355호)

○ 연사: Prof. Kyungwha Park (Department of Physics, Virginia Polytechnic Institute and State University, USA)

○ Title: Engineering and probing topological properties of Dirac semimetal films by asymmetric charge transfer

○ Abstract: 

Dirac and Weyl semimetals have been under intense investigation due to
topologically protected Weyl nodes and Fermi arc states connecting the
node projections at a surface. Recently, Na3Bi, Cd3As2, PtSe2, and PtTe2
have been experimentally confirmed to be Dirac semimetals (DSMs), where
the Dirac nodes are stabilized by crystal rotational symmetries. In the
presence of an external magnetic field, the DSMs become Weyl semimetals.
In heterostructures involving DSMs, charge transfer may occur at the
interfaces, which can be used to probe and control their bulk and surface
topological properties through surface-bulk connectivity. Here we demonstrate
that despite a band gap in thin DSM films, asymmetric charge transfer at the
surface enables one to accurately identify locations of the Dirac-node
projections from gapless band crossings and to examine and engineer properties
of the topological Fermi-arc surface states connecting the projections, by
simulating adatom-adsorbed DSM films using a first-principles method and by
comparing with the effective model. We show that as the amount of charge
transfer varies, unique spin textures near the projections and a separation
between the Fermi-arc states change. Our results can be observed by top or
bottom gating without adatoms.