14,732 research outputs found
Classical spin liquid instability driven by off-diagonal exchange in strong spin-orbit magnets
We show that the off-diagonal exchange anisotropy drives Mott insulators with
strong spin-orbit coupling to a classical spin liquid regime, characterized by
an infinite number of ground states and Ising variables living on closed or
open strings. Depending on the sign of the anisotropy, quantum fluctuations
either fail to lift the degeneracy down to very low temperatures, or select
non-collinear magnetic states with unconventional spin correlations. The
results apply to all 2D and 3D tri-coordinated materials with bond-directional
anisotropy, and provide a consistent interpretation of the suppression of the
x-ray magnetic circular dichroism signal reported recently for
-LiIrO under pressure
Critical properties of the Kitaev-Heisenberg model
We study critical properties of the Kitaev-Heisenberg model on the honeycomb
lattice at finite temperatures which might describe the physics of the quasi
two-dimensional compounds, NaIrO and LiIrO. The model undergoes
two phase transitions as a function of temperature. At low temperature, thermal
fluctuations induce magnetic long-range order by order-by-disorder mechanism.
Magnetically ordered state with the spontaneously broken symmetry
persists up to a certain critical temperature. We find that there is an
intermediate phase between the low-temperature ordered phase and the
high-temperature disordered phase. The finite-sized scaling analysis suggests
that the intermediate phase is a critical Kosterlitz-Thouless phase with
continuously variable exponents. We argue that the intermediate phase has been
actually observed above the low-temperature magnetically ordered phase in
NaIrO, and likely in LiIrO.Comment: 5 pages, 6 figure
Baryon Number Violating Transitions in String Backgrounds
We construct field configurations that interpolate between string background
states of differing baryon number. Using these configurations we estimate the
effect of the background fields on the energy barrier separating different
vacua. In the background of a superconducting GUT string the energy barrier is
increased, while in an electroweak string background or the electroweak layer
of a non-superconducting string the energy barrier is reduced. The energy
barrier depends sensitively on both the background gauge and scalar fields.Comment: 27 pages. Texing problems fixe
Spin dynamics in the generalized ferromagnetic Kondo model for manganites
Dynamical spin susceptibility is calculated for the generalized ferromagnetic
Kondo model which describes itinerant electrons interacting with
localized electrons with antiferromagnetic coupling. The calculations
done in the mean field approximation show that the spin-wave spectrum of the
system in ferromagnetic state has two branches, acoustic and optic ones.
Self-energy corrections to the spectrum are considered and the acoustic
spin-wave damping is evaluated
A method for tailoring the information content of a software process model
The framework is defined for a general method for selecting a necessary and sufficient subset of a general software life cycle's information products, to support new software development process. Procedures for characterizing problem domains in general and mapping to a tailored set of life cycle processes and products is presented. An overview of the method is shown using the following steps: (1) During the problem concept definition phase, perform standardized interviews and dialogs between developer and user, and between user and customer; (2) Generate a quality needs profile of the software to be developed, based on information gathered in step 1; (3) Translate the quality needs profile into a profile of quality criteria that must be met by the software to satisfy the quality needs; (4) Map the quality criteria to set of accepted processes and products for achieving each criterion; (5) Select the information products which match or support the accepted processes and product of step 4; and (6) Select the design methodology which produces the information products selected in step 5
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