1,603 research outputs found
Jahn-Teller like origin of the tetragonal distortion in disordered Fe-Pd magnetic shape memory alloys
The electronic structure and magnetic properties of disordered
FePd alloys are investigated in the framework
of density functional theory using the full potential local orbital method
(FPLO). Disorder is treated in the coherent potential approximation (CPA). Our
calculations explain the experimental magnetization data. The origin of the
tetragonal distortion in the Fe-Pd magnetic shape memory alloys is found to be
a Jahn-Teller like effect which allows the system to reduce its band energy in
a narrow composition range. Prospects for an optimization of the alloys'
properties by adding third elements are discussed
Engineering topological surface-states: HgS, HgSe and HgTe
Using density functional electronic structure calculations, we establish the
consequences of surface termination and modification on protected
surface-states of metacinnabar (beta-HgS). Whereas we find that the Dirac cone
is isotropic and well-separated from the valence band for the (110) surface, it
is highly anisotropic at the pure (001) surface. We demonstrate that the
anisotropy is modified by surface passivation because the topological
surface-states include contributions from dangling bonds. Such dangling bonds
exist on all pure surfaces within the whole class HgX with X = S, Se, or Te and
directly affect the properties of the Dirac cone. Surface modifications also
alter the spatial location (depth and decay length) of the topologically
protected edge-states which renders them essential for the interpretation of
photoemission data.Comment: 5 pages, 4 figure
Metacinnabar ({\beta}-HgS): a strong 3D topological insulator with highly anisotropic surface states
We establish the presence of topologically protected edge states on the (001)
surface of HgS in the zinc-blende structure using density-functional electronic
structure calculations. The Dirac point of the edge state cone is very close to
the bulk valence band maximum. The Dirac cone is extremely anisotropic with a
very large electron velocity along one diagonal of the surface elementary cell
x' and a nearly flat dispersion in the perpendicular direction y'. The strong
anisotropy originates from a broken fourfold rotoinversion symmetry at the
surface.Comment: Phys. Rev. Lett., in pres
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