833 research outputs found
Realization of Berezinskii's superconductivity in quasi-one-dimensional systems
We revisit the pairing symmetry competition in quasi-one-dimensional systems.
We show that spin-triplet s-wave pairing, where the pair is formed by electrons
with different times and has an odd-frequency symmetry, can be realized in
systems with strong one-dimensionality when the strength of charge fluctuation
dominates over spin fluctuation. The present study provides a novel microscopic
mechanism for this exotic pairing originally proposed by Berezinskii in 1974.Comment: 4 pages, 4 figure
Dynamical Generation of Non-Abelian Gauge Group via the Improved Perturbation Theory
It was suggested that the massive Yang-Mills-Chern-Simons matrix model has
three phases and that in one of them a non-Abelian gauge symmetry is
dynamically generated. The analysis was at the one-loop level around a
classical solution of fuzzy sphere type. We obtain evidences that three phases
are indeed realized as nonperturbative vacua by using the improved perturbation
theory. It also gives a good example that even if we start from a trivial
vacuum, the improved perturbation theory around it enables us to observe
nontrivial vacua.Comment: 31 pages, published versio
A unified origin for the 3D magnetism and superconductivity in NaCoO
We analyze the origin of the three dimensional (3D) magnetism observed in
nonhydrated Na-rich NaCoO within an itinerant spin picture using a 3D
Hubbard model. The origin is identified as the 3D nesting between the inner and
outer portions of the Fermi surface, which arise due to the local minimum
structure of the band at the -A line. The calculated spin wave
dispersion strikingly resembles the neutron scattering result. We argue that
this 3D magnetism and the spin fluctuations responsible for superconductivity
in the hydrated systems share essentially the same origin.Comment: 5pages, 6figure
Hole Pairs in the Two-Dimensional Hubbard Model
The interactions between holes in the Hubbard model, in the low density,
intermediate to strong coupling limit, are investigated. Dressed spin polarons
in neighboring sites have an increased kinetic energy and an enhanced hopping
rate. Both effects are of the order of the hopping integral and lead to an
effective attraction at intermediate couplings. Our results are derived by
systematically improving mean field calculations. The method can also be used
to derive known properties of isolated spin polarons.Comment: 4 page
Superconducting Fluctuations in a Multi-Band 1D Hubbard Model
A renormalization-group and bosonization approach for a multi-band Hubbard
Hamiltonian in one dimension is described. Based on the limit of many bands, it
is argued that this Hamiltonian with bare repulsive electron-electron
interactions is scaled under specific conditions to a model in which
superconducting fluctuations dominate.Comment: 12 pages + 1 fig, Revtex, Preprint - Los Alamo
Spin-fluctuation exchange study of superconductivity in two- and three-dimensional single-band Hubbard models
In order to identify the most favorable situation for superconductivity in
the repulsive single-band Hubbard model, we have studied instabilities for
d-wave pairing mediated by antiferromagnetic spin fluctuations and p-pairing
mediated by ferromagnetic fluctuations with the fluctuation exchange
approximation in both two dimensions and three dimensions. By systematically
varying the band filling and band structure we have shown that (i) d-pairing is
stronger in two dimensions than in three dimensions, and (ii) p-pairing is much
weaker than the d-pairing.Comment: RevTex, 5 figures in Postscript, to be published in Phys. Rev.
Renormalization Group Technique Applied to the Pairing Interaction of the Quasi-One-Dimensional Superconductivity
A mechanism of the quasi-one-dimensional (q1d) superconductivity is
investigated by applying the renormalization group techniques to the pairing
interaction. With the obtained renormalized pairing interaction, the transition
temperature Tc and corresponding gap function are calculated by solving the
linearized gap equation. For reasonable sets of parameters, Tc of p-wave
triplet pairing is higher than that of d-wave singlet pairing due to the
one-dimensionality of interaction. These results can qualitatively explain the
superconducting properties of q1d organic conductor (TMTSF)2PF6 and the ladder
compound Sr2Ca12Cu24O41.Comment: 18 pages, 9 figures, submitted to J. Phys. Soc. Jp
Avaliação por FTIR da matéria orgânica presente em efluente tratado em biodigestor anaeróbio visando sua aplicação como fertilizante na agricultura.
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