TY  - JOUR
A1  - Varykhalov, A.
A1  - Marchenko, D.
A1  - Sánchez-Barriga, J.
A1  - Scholz, M. R.
A1  - Verberck, B.
A1  - Trauzettel, B.
A1  - Wehling, T. O.
A1  - Carbone, C.
A1  - Rader, O.
T1  - Intact Dirac Cones at Broken Sublattice Symmetry: Photoemission Study of Graphene on Ni and Co
JF  - Physical Review X
N2  - The appearance of massless Dirac fermions in graphene requires two equivalent carbon sublattices of trigonal shape. While the generation of an effective mass and a band gap at the Dirac point remains an unresolved problem for freestanding extended graphene, it is well established by breaking translational symmetry by confinement and by breaking sublattice symmetry by interaction with a substrate. One of the strongest sublattice-symmetry-breaking interactions with predicted and measured band gaps ranging from 400 meV to more than 3 eV has been attributed to the interfaces of graphene with Ni and Co, which are also promising spin-filter interfaces. Here, we apply angle-resolved photoemission to epitaxial graphene on Ni (111) and Co(0001) to show the presence of intact Dirac cones 2.8 eV below the Fermi level. Our results challenge the common belief that the breaking of sublattice symmetry by a substrate and the opening of the band gap at the Dirac energy are in a straightforward relation. A simple effective model of a biased bilayer structure composed of graphene and a sublattice-symmetry-broken layer, corroborated by density-functional-theory calculations, demonstrates the general validity of our conclusions.
KW  - NI(111)
KW  - ultrasoft pseudopotentials
KW  - monolayer graphite
KW  - electronic states
KW  - transistors
KW  - surface
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-135732
VL  - 2
IS  - 041017
ER  - 
TY  - JOUR
A1  - Weiße, Sebastian
A1  - Heddergott, Niko
A1  - Heydt, Matthias
A1  - Pflästerer, Daniel
A1  - Maier, Timo
A1  - Haraszti, Tamas
A1  - Grunze, Michael
A1  - Engstler, Markus
A1  - Rosenhahn, Axel
T1  - A Quantitative 3D Motility Analysis of Trypanosoma brucei by Use of Digital In-line Holographic Microscopy
JF  - PLoS One
N2  - We present a quantitative 3D analysis of the motility of the blood parasite Trypanosoma brucei. Digital in-line holographic microscopy has been used to track single cells with high temporal and spatial accuracy to obtain quantitative data on their behavior. Comparing bloodstream form and insect form trypanosomes as well as mutant and wildtype cells under varying external conditions we were able to derive a general two-state-run-and-tumble-model for trypanosome motility. Differences in the motility of distinct strains indicate that adaption of the trypanosomes to their natural environments involves a change in their mode of swimming.
KW  - african trypanosomes
KW  - actin cortex
KW  - flagellum
KW  - tracking
KW  - surface
KW  - models
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130666
VL  - 7
IS  - 5
ER  -