188 research outputs found
Possible Realization and Protection of Valley-Polarized Quantum Hall Effect in Mn/WS2
By using the first-principles calculations and model analyses, we found that
the combination of defected tungsten disulfide monolayer and sparse manganese
adsorption may give a KK` valley spin splitting up to 210 meV. This system also
has a tunable magnetic anisotropy energy, a clean band gap, and an appropriate
band alignment, with the Fermi level sitting right above the top of valence
bands at the K-valleys. Therefore, it can be used for the realization of the
valley-polarized anomalous Hall effect and for the exploration of other valley
related physics without using optical methods. A protective environment can be
formed by covering it with a hexagonal BN layer, without much disturbance to
the benign properties of Mn/WS2.Comment: 16 pages, 4 figure
Thioglycolic acid on the gold (111) surface and Raman vibrational spectra
The interaction of thioglycolic acid with the Au(111) surface is
investigaged, and it is found that at the low coverage the molecule lies down
on the substrate. If the mercaptan-hydrogen atom is eliminated, the resulting
SCH_2COOH molecule is randomly oriented on the surface. If the carboxylic acid
group in the HSCH_2COOH molecule is deprotonated instead, the HSCH_2COO^
molecule lies down on the surface. However, when the mercaptan-hydrogen atom in
the HSCH_2COO^- molecule is removed, the resulting SCH_2COO^- molecule rises up
to a certain level on the substrate. The calculated Raman vibrational spectra
decipher which compounds and atomic displacements contribute to the
corresponding frequencies. We thus propose a consistent mechanism for the
deposition of thioglycolic acid on the Au(111) surface.Comment: 18 pages, 5 figures, submitted to J. Chem. Phy
Giant topological insulator gap in graphene with 5d adatoms
Two-dimensional topological insulators (2D TIs) have been proposed as
platforms for many intriguing applications, ranging from spintronics to
topological quantum information processing. Realizing this potential will
likely be facilitated by the discovery of new, easily manufactured materials in
this class. With this goal in mind we introduce a new framework for engineering
a 2D TI by hybridizing graphene with impurity bands arising from heavy adatoms
possessing partially filled d-shells, in particular osmium and iridium. First
principles calculations predict that the gaps generated by this means exceed
0.2 eV over a broad range of adatom coverage; moreover, tuning of the Fermi
level is not required to enter the TI state. The mechanism at work is expected
to be rather general and may open the door to designing new TI phases in many
materials.Comment: 7 pages, 8 figure
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