13,598 research outputs found
Absence of a true long-range orbital order in a two-leg Kondo ladder
We investigate, through the density-matrix renormalization group and the
Lanczos technique, the possibility of a two-leg Kondo ladder present an
incommensurate orbital order. Our results indicate a staggered short-range
orbital order at half-filling. Away from half-filling our data are consistent
with an incommensurate quasi-long-range orbital order. We also observed that an
interaction between the localized spins enhances the rung-rung current
correlations.Comment: 7 pages, 6 figures, changed the introduction and added some
discussion
The dipole anisotropy of WISE x SuperCOSMOS number counts
We probe the isotropy of the Universe with the largest all-sky photometric
redshift dataset currently available, namely WISE~~SuperCOSMOS. We
search for dipole anisotropy of galaxy number counts in multiple redshift
shells within the range, for two subsamples drawn from the
same parent catalogue. Our results show that the dipole directions are in good
agreement with most of the previous analyses in the literature, and in most
redshift bins the dipole amplitudes are well consistent with CDM-based
mocks in the cleanest sample of this catalogue. In the range, however,
we obtain a persistently large anisotropy in both subsamples of our dataset.
Overall, we report no significant evidence against the isotropy assumption in
this catalogue except for the lowest redshift ranges. The origin of the latter
discrepancy is unclear, and improved data may be needed to explain it.Comment: 5 pages, 4 figures, 2 tables. Published in MNRA
Coexistence of Pairing Tendencies and Ferromagnetism in a Doped Two-Orbital Hubbard Model on Two-Leg Ladders
Using the Density Matrix Renormalization Group and two-leg ladders, we
investigate an electronic two-orbital Hubbard model including plaquette
diagonal hopping amplitudes. Our goal is to search for regimes where charges
added to the undoped state form pairs, presumably a precursor of a
superconducting state.For the electronic density , i.e. the undoped
limit, our investigations show a robust antiferromagnetic ground
state, as in previous investigations. Doping away from and for large
values of the Hund coupling , a ferromagnetic region is found to be stable.
Moreover, when the interorbital on-site Hubbard repulsion is smaller than the
Hund coupling, i.e. for in the standard notation of multiorbital Hubbard
models, our results indicate the coexistence of pairing tendencies and
ferromagnetism close to . These results are compatible with previous
investigations using one dimensional systems. Although further research is
needed to clarify if the range of couplings used here is of relevance for real
materials, such as superconducting heavy fermions or pnictides, our theoretical
results address a possible mechanism for pairing that may be active in the
presence of short-range ferromagnetic fluctuations.Comment: 8 pages, 4 Fig
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