666 research outputs found
Impurity-induced smearing of the spin resonance peak in Fe-based superconductors
The spin resonance peak in the iron-based superconductors is observed in
inelastic neutron scattering experiments and agrees well with predicted results
for the extended s-wave () gap symmetry. On the basis of four-band and
three-orbital tight binding models we study the effect of nonmagnetic disorder
on the resonance peak. Spin susceptibility is calculated in the random phase
approximation with the renormalization of the quasiparticle self-energy due to
the impurity scattering in the static Born approximation. We find that the spin
resonance becomes broader with the increase of disorder and its energy shifts
to higher frequencies. For the same amount of disorder the spin response in the
state is still distinct from that of the state.Comment: 4 pages, 2 figure
Nonmatrix varieties of nonassociative algebras
A variety of associative algebras is called nonmatrix if it does not contain
the algebra of 2 x 2 matrices over the given field. Nonmatrix varieties were
introduced and studied by V.N.Latyshev in relation with the Specht problem.
Some characterizations of nonmatrix varieties were obtained in the paper [10].
In the given paper the notion of nonmatrix variety is extended for
nonassociative algebras, and the characterization from [10] is generalized for
alternative, Jordan, and some other varieties of algebras
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