2,550 research outputs found
Spin-charge separation in Aharonov-Bohm rings of interacting electrons
We investigate the properties of strongly correlated electronic models on a
flux-threaded ring connected to semi-infinite free-electron leads. The
interference pattern of such an Aharonov-Bohm ring shows sharp dips at certain
flux values, determined by the filling, which are a consequence of spin-charge
separation in a nanoscopic system.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let
Superconductivity with s and p-symmetries in an extended Hubbard model with correlated hopping
We consider a generalized Hubbard model with on-site and nearest-neighbour
repulsions U and V respectively, and nearest-neighbour hopping for spin up
(down) which depends on the total occupation n_b of spin down (up) electrons on
both sites involved. The hopping parameters are t_{AA}, t_{AB} and t_{BB} for
n_b=0,1,2 respectively. We briefly summarize results which support that the
model exhibits s-wave superconductivity for certain parameters and extend them
by studying the Berry phases. Using a generalized Hartree-Fock(HF) BCS
decoupling of the two and three-body terms, we obtain that at half filling, for
t_{AB}<t_{AA}=t_{BB} and sufficiently small U and V the model leads to triplet
p-wave superconductivity for a simple cubic lattice in any dimension. In one
dimension, the resulting phase diagram is compared with that obtained
numerically using two quantized Berry phases (topological numbers) as order
parameters. While this novel method supports the previous results, there are
quantitative differences.Comment: Latex file, 14 pages, 2 postscript figure
Application of ERTS-1 Imagery to Flood Inundation Mapping
Application of ERTS-1 imagery to flood inundation mapping in East and West Nishnabotna basins of southwestern Iow
Critical behavior of the S=3/2 antiferromagnetic Heisenberg chain
Using the density-matrix renormalization-group technique we study the
long-wavelength properties of the spin S=3/2 nearest-neighbor Heisenberg chain.
We obtain an accurate value for the spin velocity v=3.8+- 0.02, in agreement
with experiment. Our results show conclusively that the model belongs to the
same universality class as the S=1/2 Heisenberg chain, with a conformal central
charge c=1 and critical exponent eta=1Comment: RevTeX (version 3.0), 4 twocolumn pages with 4 embedded figure
Spin-spin correlations between two Kondo impurities coupled to an open Hubbard chain
In order to study the interplay between Kondo and
Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, we calculate the spin-spin
correlation functions between two Kondo impurities coupled to different sites
of a half-filled open Hubbard chain. Using the density-matrix renormalization
group (DMRG), we re-examine the exponents for the power-law decay of the
correlation function between the two impurity spins as a function of the
antiferromagnetic coupling J, the Hubbard interaction U, and the distance R
between the impurities. The exponents for finite systems obtained in this work
deviate from previously published DMRG calculations. We furthermore show that
the long-distance behavior of the exponents is the same for impurities coupled
to the bulk or to both ends of the chain. We note that a universal exponent for
the asymptotic behavior cannot be extracted from these finite-size systems with
open boundary conditions.Comment: 8 pages, 10 figures; v2: final version, references and Fig. 8 adde
Quantum correlations in nanostructured two-impurity Kondo systems
We study the ground-state entanglement properties of nanostructured Kondo
systems consisting of a pair of impurity spins coupled to a background of
confined electrons. The competition between the RKKY-like coupling and the
Kondo effect determines the development of quantum correlations between the
different parts of the system. A key element is the electronic filling due to
confinement. An even electronic filling leads to results similar to those found
previously for extended systems, where the properties of the reduced
impurity-spin subsystem are uniquely determined by the spin correlation
function defining a one-dimensional phase space. An odd filling, instead,
breaks spin-rotation symmetry unfolding a two-dimensional phase space showing
rich entanglement characteristics as, e.g., the requirement of a larger amount
of entanglement for the development of non-local correlations between impurity
spins. We check these results by numerical simulations of elliptic quantum
corrals with magnetic impurities at the foci as a case study.Comment: Submitted for publication. 8 pages, 4 figures. Revised versio
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