16 research outputs found
Low-Energy Spin Dynamics of CuO Chains in YBa(2)Cu(3)O(6+x)
We study the spin fluctuation dynamics of Cu-O chains in the oxygen deficient
planes of YBa(2)Cu(3)O(6+x). The chains are described by a model including
antiferromagnetic interactions between the spins and Kondo-like scattering of
the oxygen holes by the copper spins. There are incommensurate spin
fluctuations along the direction of the chains. The dynamic structure factor of
this system is qualitatively different from that of a quasi one-dimensional
localized antiferromagnet due to the presence of itinerant holes. We compute
the dynamic structure factor that could be measured in neutron scattering
experiments.Comment: 2 pages, 2 eps figures, LT22 proceedings, phbauth style file include
Dzyaloshinskii-Moriya interaction in the paramagnetic state and the polarized neutron scattering
Dzyaloshinskii-Moriya (DM) interaction in the paramagnetic state leads to the
incommensurate spin fluctuations with incommensurate vector proportional to the
relative strength of the DM interaction. We show that the DM interaction leads
to helical spin fluctuations which may be observed by the polarized neutron
scattering.Comment: 4 pages, no figures, PNCMI-2000 proceedings, phbauth style file
ecnlose
RKKY interaction in the nearly-nested Fermi liquid
We present the results of analytical evaluation of the indirect RKKY
interaction in a layered metal with nearly nested (almost squared) Fermi
surface. The final expressions are obtained in closed form as a combination of
Bessel functions. We discuss the notion of the
``2k_F'' oscillations and show that they occur as the far asymptote of our
expressions. We show the existence of the intermediate asymptote of the
interaction which is of the sign-reversal antiferromagnetic type and is the
only term surviving in the limit of exact nesting. A good accordance of our
analytical formulas with numerical findings is demonstrated until the
interatomic distances. The obtained expressions for the Green's functions
extend the previous analytical results into the region of intermediate
distances as well.Comment: 9 pages, REVTEX, 3 .eps figures, to appear in PRB 1 Oct 199
Optical conductivity of one-dimensional doped Hubbard-Mott insulator
We study the optical response of a strongly correlated electron system near
the metal-insulator transition using a mapping to the sine-Gordon model. With
semiclassical quantization, the spectral weight is distributed between a Drude
peak and absorption lines due to breathers. We calculate the Drude weight, the
optical gap, and the lineshape of breather absorption.Comment: 4 pages, 2 EPS figures, REVTEX 4, a final versio
Optical Sum Rule in Finite Bands
In a single finite electronic band the total optical spectral weight or
optical sum carries information on the interactions involved between the charge
carriers as well as on their band structure. It varies with temperature as well
as with impurity scattering. The single band optical sum also bears some
relationship to the charge carrier kinetic energy and, thus, can potentially
provide useful information, particularly on its change as the charge carriers
go from normal to superconducting state. Here we review the considerable
advances that have recently been made in the context of high oxides, both
theoretical and experimental.Comment: Review article accepted for publication in J. Low Temp. Phys. 29
pages, 33 figure
Ferromagnetism and Canted Spin Phase in AlAs/GaMnAs Single Quantum Wells: Monte Carlo Simulation
The magnetic order resulting from a confinement-adapted
Ruderman-Kittel-Kasuya-Yosida indirect exchange between magnetic moments in the
metallic phase of a AlAs/Ga(1-x)Mn(x)As quantum well is studied by Monte Carlo
simulation. This coupling mechanism involves magnetic moments and carriers
(holes), both coming from the same Mn(2+) ions. It leads to a paramagnetic, a
ferromagnetic, or a canted spin phase, depending on the carrier concentration,
and on the magnetic layer width. It is shown that high transition temperatures
may be obtained.Comment: 7 figure
1D Frustrated Ferromagnetic Model with Added Dzyaloshinskii-Moriya Interaction
The one-dimensional (1D) isotropic frustrated ferromagnetic spin-1/2 model is
considered. Classical and quantum effects of adding a Dzyaloshinskii-Moriya
(DM) interaction on the ground state of the system is studied using the
analytical cluster method and numerical Lanczos technique. Cluster method
results, show that the classical ground state magnetic phase diagram consists
of only one single phase: "chiral". The quantum corrections are determined by
means of the Lanczos method and a rich quantum phase diagram including the
gapless Luttinger liquid, the gapped chiral and dimer orders is obtained.
Moreover, next nearest neighbors will be entangled by increasing DM interaction
and for open chains, end-spins are entangled which shows the long distance
entanglement (LDE) feature that can be controlled by DM interaction.Comment: 8 pages, 9 figure
Ginzburg-Landau functional for nearly antiferromagnetic perfect and disordered Kondo lattices
Interplay between Kondo effect and trends to antiferromagnetic and spin glass
ordering in perfect and disordered bipartite Kondo lattices is considered.
Ginzburg-Landau equation is derived from the microscopic effective action
written in three mode representation (Kondo screening, antiferromagnetic
correlations and spin liquid correlations). The problem of local constraint is
resolved by means of Popov-Fedotov representation for localized spin operators.
It is shown that the Kondo screening enhances the trend to a spin liquid
crossover and suppresses antiferromagnetic ordering in perfect Kondo lattices
and spin glass ordering in doped Kondo lattices. The modified Doniach's diagram
is constructed, and possibilities of going beyond the mean field approximation
are discussed.Comment: 18 pages, RevTeX, 7 EPS figures include
On the inverse problem for the multiple small-angle neutron scattering
Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal