TY  - JOUR
A1  - Fleszar, Andrzej
A1  - Hanke, Werner
T1  - Two-dimensional metallicity with a large spin-orbit splitting: DFT calculations of the atomic, electronic, and spin structures of the Au/Ge(111)-(√3 x √3)R30° surface
JF  - Advances in Condensed Matter Physics
N2  - Density functional theory (DFT) is applied to study the atomic, electronic, and spin structures of the Au monolayer at the Ge(111) surface. It is found that the theoretically determined most stable atomic geometry is described by the conjugated honeycomb-chained-trimer (CHCT) model, in a very good agreement with experimental data. The calculated electronic structure of the system, being in qualitatively good agreement with the photoemission measurements, shows fingerprints of the many-body effects (self-interaction corrections) beyond the LDA or GGA approximations. The most interesting property of this surface system is the large spin splitting of its metallic surface bands and the undulating spin texture along the hexagonal Fermi contours, which highly resembles the spin texture at the Dirac state of the topological insulator Bi\(_{2}\)Te\(_{3}\). These properties make this system particularly interesting from both fundamental and technological points of view.
KW  - topological insulators
KW  - gas
KW  - density functional theory
KW  - conjugated honeycomb-chained-trimer
KW  - spin structures
KW  - Au/Ge(111)
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149221
VL  - 2015
IS  - 531498
ER  - 
TY  - JOUR
A1  - Kim, N. Y.
A1  - Kusudo, K.
A1  - Löffler, A.
A1  - Höfling, S.
A1  - Forchel, A.
A1  - Yamamoto, Y.
T1  - Exciton-polariton condensates near the Dirac point in a triangular lattice
JF  - New Journal of Physics
N2  - Dirac particles, massless relativistic entities, obey linear energy dispersions and hold important implications in particle physics. The recent discovery of Dirac fermions in condensed matter systems including graphene and topological insulators has generated a great deal of interest in exploring the relativistic properties associated with Dirac physics in solid-state materials. In addition, there are stimulating research activities to engineer Dirac particles, elucidating their exotic physical properties in a controllable setting. One of the successful platforms is the ultracold atom-optical lattice system, whose dynamics can be manipulated and probed in a clean environment. A microcavity exciton-polariton-lattice system offers the advantage of forming high-orbital condensation in non-equilibrium conditions, which enables one to explore novel quantum orbital order in two dimensions. In this paper, we experimentally construct the band structures near Dirac points, the vertices of the first hexagonal Brillouin zone with exciton-polariton condensates trapped in a triangular lattice. Due to the finite spectral linewidth, the direct map of band structures at Dirac points is elusive; however, we identify the linear part above Dirac points and its associated velocity value is similar to ~0.9-2 x \(10^8 cm s^{-1}\), consistent with the theoretical estimate \(1 x 10^8 cm s^{-1}\) with a \(2 \mu m\) lattice constant. We envision that the exciton-polariton condensates in lattices would be a promising solid-state platform, where the system order parameter can be accessed in both real and momentum spaces.
KW  - Bose-Einstein condensation
KW  - carbon nanotubes
KW  - graphene
KW  - electron
KW  - dynamics
KW  - fermions
KW  - trap
KW  - gas
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-123103
SN  - 1367-2630
VL  - 15
IS  - 035032
ER  -