34,788 research outputs found
Vortices in the presence of a nonmagnetic atom impurity in 2D XY ferromagnets
Using a model of nonmagnetic impurity potential, we have examined the
behavior of planar vortex solutions in the classical two-dimensional XY
ferromagnets in the presence of a spin vacancy localized out of the vortex
core. Our results show that a spinless atom impurity gives rise to an effective
potential that repels the vortex structure.Comment: 6 pages, 2 figures, RevTex
Orthogonality catastrophe and Kondo effect in graphene
Anderson's orthogonality catastrophe in graphene, at energies close to the
Dirac point, is analyzed. It is shown that, in clean systems, the orthogonality
catastrophe is suppressed, due to the vanishing density of states at the Dirac
point. In the presence of preexisting localized states at the Dirac energy, the
orthogonality catastrophe shows similar features to those found in normal
metals with a finite density of states at the Fermi level. The implications for
the Kondo effect induced by magnetic impurities, and for the Fermi edge
singularities in tunneling processes are also discussed.Comment: 7 pages, 7 figure
Exact edge singularities and dynamical correlations in spin-1/2 chains
Exact formulas for the singularities of the dynamical structure factor,
S^{zz}(q,omega), of the S=1/2 xxz spin chain at all q and any anisotropy and
magnetic field in the critical regime are derived, expressing the exponents in
terms of the phase shifts which are known exactly from the Bethe ansatz
solution. We also study the long time asymptotics of the self-correlation
function . Utilizing these results to supplement very
accurate time-dependent Density Matrix Renormalization Group (DMRG) for short
to moderate times, we calculate S^{zz}(q,omega) to very high precision.Comment: 4 pages, 1 figure, 1 table, published versio
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