6,347 research outputs found
Collective Modes in the Loop Current Ordered Phase of Cuprates
Recently two branches of weakly dispersive collective modes have been
discovered in under-doped cuprates by inelastic neutron scattering.
Polarization analysis reveals that the modes are magnetic excitations. They are
only visible for temperatures below the transition temperature to a broken
symmetry phase which was discovered earlier and their intensity increases as
temperature is further decreased. The broken symmetry phase itself has
symmetries consistent with ordering of orbital current loops within a unit-cell
without breaking translational symmetry. In order to calculate the collective
modes of such a state we add quantum terms to the Ashkin-Teller (AT) model with
which the classical loop current order has been described. We derive that the
mean field ground state of the quantum model is a product over all unit-cells
of linear combination of the four possible classical configurations of the loop
current order in each unit-cell. The collective modes are calculated by using a
generalized Holstein-Primakoff boson representation of orbital moment operators
and lead to three branches of gapped weakly dispersive collective modes. The
experimental results are consistent with the two lower energy branches; the
third mode is at a higher energy than looked for by present neutron scattering
experiments and might also be over-damped. Implications of the discovery of the
collective modes are discussed.Comment: 16 pages, 6 figure
Heavy-Fermions in a Transition-Metal Compound:
The recent discovery of heavy-Fermion properties in Lithium Vanadate and the
enormous difference in its properties from the properties of Lithium Titanate
as well as of the manganite compounds raise some puzzling questions about
strongly correlated Fermions. These are disscussed as well as a solution to the
puzzles provided.Comment: late
A Data Structure for Spatio-Temporal Databases
The advantages and applications of spatial mechanisms are well documented; however, there are very few being designed. The principal hinderance to the design of spatial mechanisms is the great difficulty involved in specifying spatial problems and in interpreting spatial solutions. Similarly, the development of spatial codes to implement these techniques is held back by the lack of means to easily visualize and verify solutions, particularly in the realm of relational databases. If spatial mechanisms are to be successful, the designer must be able to synthesize, analyse and evaluate, as well as load and extract information, using a single code representing a spatial structure. This entails the implementation of spatial relationships involving spatial data structures. It is with this in mind that the Canadian Hydrographic Service database group embarked on the development of a new type of spatial database structure based on the quadtree concept
Only Fermi-Liquids are Metals
Any singular deviation from Landau Fermi-liquid theory appears to lead, for
arbitrarily small concentration of impurities coupling to a non-conserved
quantity, to a vanishing density of states at the chemical potential and
infinite resistivity as temperature approaches zero. Applications to
copper-oxide metals including the temperature dependence of the anisotropy in
resistivity, and to other cases of non Fermi-liquids are discussed.Comment: 11 pages,revtex, 1 Postscript figur
Single intra-articular steroid injection of the glenohumeral joint in management of adhesive capsulitis: a comparison between approaches
Background: Adhesive capsulitis is a common, painful musculoskeletal condition of the shoulder associated with loss of range of motion in the glenohumeral joint resulting from contraction of the glenohumeral joint capsule and adherence to the humeral head. Earlier stages of adhesive capsulitis can be treated by intra-articular steroid injections into the glenohumeral joint. This study was designed to study the role of long acting intra-articular corticosteroid injections in combination with simple therapeutic exercises while comparing the outcome of blinded anterior and posterior injection approaches in the management of adhesive capsulitis.Methods: The study comprised of 60 subjects aged 18 years and above who were diagnosed with primary adhesive capsulitis. They were randomly divided into 2 groups i.e., Group A who received blind intra-articular steroid injections via standard anterior approach and group B who received blind intra-articular steroid injection via standard posterior approach. Both groups followed up with a simple home based exercise program. Outcome measures assessed were visual analog scale (VAS) score, shoulder pain assessment disability index (SPADI) and passive shoulder range of motion (ROM).Results: At last follow up, both groups showed statistically significant improvements in all outcome measures i.e., VAS score, SPADI, shoulder ROM. However, comparison between groups did not reveal any statistically significant differences between the two groups.Conclusions: Intra-articular steroid injections into the glenohumeral joint in conjunction with simple physiotherapy are effective in improving pain, function and shoulder ROM in adhesive capsulitis. Both the anterior and posterior injection approaches provide good results
Effective Lorentz Force due to Small-angle Impurity Scattering: Magnetotransport in High-Tc Superconductors
We show that a scattering rate which varies with angle around the Fermi
surface has the same effect as a periodic Lorentz force on magnetotransport
coefficients. This effect, together with the marginal Fermi liquid inelastic
scattering rate gives a quantitative explanation of the temperature dependence
and the magnitude of the observed Hall effect and magnetoresistance with just
the measured zero-field resistivity as input.Comment: 4 pages, latex, one epsf figure included in text. Several revisions
and corrections are included. Major conclusions are the sam
Staggered Flux Phase in a Model of Strongly Correlated Electrons
We present numerical evidence for the existence of a staggered flux (SF)
phase in the half-filled two-leg t-U-V-J ladder, with true long-range order in
the counter-circulating currents. The density-matrix renormalization-group
(DMRG) / finite-size scaling approach, generalized to describe complex-valued
Hamiltonians and wavefunctions, is employed. The SF phase exhibits robust
currents at intermediate values of the interaction strength.Comment: Version to appear in Phys. Rev. Let
Charge Dynamics in Cuprate Superconductors
In this lecture we present some interesting issues that arise when the
dynamics of the charge carriers in the CuO planes of the high temperature
superconductors is considered. Based on the qualitative picture of doping, set
by experiments and some previous calculations, we consider the strength of
various inter and intra-cell charge transfer susceptibilities, the question of
Coulomb screening and charge collective modes. The starting point is the usual
p-d model extended by the long range Coulomb (LRC) interaction. Within this
model it is possible to examine the case in which the LRC forces frustrate the
electronic phase separation, the instability which is present in the model
without an LRC interaction. While the static dielectric function in such
systems is negative down to arbitrarily small wavevectors, the system is not
unstable. We consider the dominant electronic charge susceptibilities and
possible consequences for the lattice properties.Comment: 14 pages, 15 figures, latex, to be published in "From Quantum
Mechanics to Technology", Lecture Notes in Physics, Springe
Nanoscale Defect Formation on InP(111) Surfaces after MeV Sb Implantation
We have studied the surface modifications as well as the surface roughness of
the InP(111) surfaces after 1.5 MeV Sb ion implantations. Scanning Probe
Microscope (SPM) has been utilized to investigate the ion implanted InP(111)
surfaces. We observe the formation of nanoscale defect structures on the InP
surface. The density, height and size of the nanostructures have been
investigated here as a function of ion fluence. The rms surface roughness, of
the ion implanted InP surfaces, demonstrates two varied behaviors as a function
of Sb ion fluence. Initially, the roughness increases with increasing fluence.
However, after a critical fluence the roughness decreases with increasing
fluence. We have further applied the technique of Raman scattering to
investigate the implantation induced modifications and disorder in InP. Raman
Scattering results demonstrate that at the critical fluence, where the decrease
in surface roughness occurs, InP lattice becomes amorphous.Comment: 18 pages, 9 figure
On The Multichannel Kondo Model"
A detailed and comprehensive study of the one-impurity multichannel Kondo
model is presented. In the limit of a large number of conduction electron
channels , the low energy fixed point is accessible to a
renormalization group improved perturbative expansion in . This
straightforward approach enables us to examine the scaling, thermodynamics and
dynamical response functions in great detail and make clear the following
features: i) the criticality of the fixed point; ii) the universal non-integer
degeneracy; iii) that the compensating spin cloud has the spatial extent of the
order of one lattice spacing.Comment: 28 pages, REVTEX 2.0. Submitted to J. Phys.: Cond. Mat. Reference
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