327,803 research outputs found
Quasiparticle scattering in two dimensional helical liquid
We study the quasiparticle interference (QPI) patterns caused by scattering
off nonmagnetic, magnetic point impurities, and edge impurities, separately, in
a two dimensional helical liquid, which describes the surface states of a
topological insulator. The unique features associated with hexagonal warping
effects are identified in the QPI patterns of charge density with nonmagnetic
impurities and spin density with magnetic impurities. The symmetry properties
of the QPI patterns can be used to determine the symmetry of microscopic
models. The Friedel oscillation is calculated for edge impurities and the decay
of the oscillation is not universal, strongly depending on Fermi energy. Some
discrepancies between our theoretical results and current experimental
observations are discussed.Comment: 12 pages, appendices added. Accepted for publication in Physical
Review B (submitted, October 2009
Anomalous diffusion, clustering, and pinch of impurities in plasma edge turbulence
The turbulent transport of impurity particles in plasma edge turbulence is
investigated. The impurities are modeled as a passive fluid advected by the
electric and polarization drifts, while the ambient plasma turbulence is
modeled using the two-dimensional Hasegawa--Wakatani paradigm for resistive
drift-wave turbulence. The features of the turbulent transport of impurities
are investigated by numerical simulations using a novel code that applies
semi-Lagrangian pseudospectral schemes. The diffusive character of the
turbulent transport of ideal impurities is demonstrated by relative-diffusion
analysis of the evolution of impurity puffs. Additional effects appear for
inertial impurities as a consequence of compressibility. First, the density of
inertial impurities is found to correlate with the vorticity of the electric
drift velocity, that is, impurities cluster in vortices of a precise
orientation determined by the charge of the impurity particles. Second, a
radial pinch scaling linearly with the mass--charge ratio of the impurities is
discovered. Theoretical explanation for these observations is obtained by
analysis of the model equations.Comment: This article has been submitted to Physics of Plasmas. After it is
published, it will be found at http://pop.aip.org/pop
Multichannel Kondo impurities in superconductors
We discuss the effect of multichannel Kondo impurities on superconductivity.
In the strong coupling regime such impurities are pairbreakers, in contrast to
the ordinary Kondo effect. Measurements of -suppression may help in
identifying impurities displaying this more exotic exchange coupling to the
conduction band.Comment: 3 pages, 4 figures, uuencoded compressed postscript file, submitted
to SCES'94 (Amsterdam
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