91 research outputs found
Electron Spin Resonance of SrCu2(BO3)2 at High Magnetic Field
We calculate the electron spin resonance (ESR) spectra of the
quasi-two-dimensional dimer spin liquid SrCu2(BO3)2 as a function of magnetic
field B. Using the standard Lanczos method, we solve a Shastry-Sutherland
Hamiltonian with additional Dzyaloshinsky-Moriya (DM) terms which are crucial
to explain different qualitative aspects of the ESR spectra. In particular, a
nearest-neighbor DM interaction with a non-zero D_z component is required to
explain the low frequency ESR lines for B || c. This suggests that crystal
symmetry is lowered at low temperatures due to a structural phase transition.Comment: 4 pages, 4 b&w figure
Fermion kinetics in the Falicov-Kimball limit of the three-band Emery model
The three-band Emery model is reduced to a single-particle quantum model of
Falicov-Kimball type, by allowing only up-spins to hop, and forbidding double
occupation by projection. It is used to study the effects of geometric
obstruction on mobile fermions in thermodynamic equilibrium. For low hopping
overlap, there appears a plateau in the entropy, due to charge correlations,
and related to real-space disorder. For large overlap, the equilibrium
thermopower susceptibility remains anomalous, with a sign opposite to the one
predicted from the single-particle density of states. The heat capacity and
non-Fermi liquid response are discussed in the context of similar results in
the literature. All results are obtained by evaluation of an effective
single-particle free-energy operator in closed form. The method to obtain this
operator is described in detail.Comment: New calculations, method explained in detail, 16 pages, 9 figure
Towards intelligent distributed computing : cell-oriented computing
Distributed computing systems are of huge importance in a number of recently established and future functions in computer science. For example, they are vital to banking applications, communication of electronic systems, air traffic control, manufacturing automation, biomedical operation works, space monitoring systems and robotics information systems. As the nature of computing comes to be increasingly directed towards intelligence and autonomy, intelligent computations will be the key for all future applications. Intelligent distributed computing will become the base for the growth of an innovative generation of intelligent distributed systems. Nowadays, research centres require the development of architectures of intelligent and collaborated systems; these systems must be capable of solving problems by themselves to save processing time and reduce costs. Building an intelligent style of distributed computing that controls the whole distributed system requires communications that must be based on a completely consistent system. The model of the ideal system to be adopted in building an intelligent distributed computing structure is the human body system, specifically the body’s cells. As an artificial and virtual simulation of the high degree of intelligence that controls the body’s cells, this chapter proposes a Cell-Oriented Computing model as a solution to accomplish the desired Intelligent Distributed Computing system
Microscopic modelling of doped manganites
Colossal magneto-resistance manganites are characterised by a complex
interplay of charge, spin, orbital and lattice degrees of freedom. Formulating
microscopic models for these compounds aims at meeting to conflicting
objectives: sufficient simplification without excessive restrictions on the
phase space. We give a detailed introduction to the electronic structure of
manganites and derive a microscopic model for their low energy physics.
Focussing on short range electron-lattice and spin-orbital correlations we
supplement the modelling with numerical simulations.Comment: 20 pages, 10 figs, accepted for publ. in New J. Phys., Focus issue on
Orbital Physic
Numerical study of the Jahn-Teller polaron and bipolaron
The properties of the polaron and bipolaron are explored in the 1D
Jahn-Teller model with dynamical quantum phonons. The ground-state properties
of the polaron and bipolaron are computed using a recently developed
variational method. Dynamical properties of the ground state of a polaron are
investigated by calculating the optical conductivity . Our
numerical results suggest that the Jahn-Teller and Holstein polarons are
similar. However, in the strong-coupling regime qualitative differences in
between the two models are found and discussed. The influence
of the electron-phonon coupling and the electrostatic repulsion on the
bipolaron binding energy, bipolaron masses, and correlation functions is
investigated.Comment: 9 pages including 11 figures. To appear in PR
Assessment of the Linkages and Leakages in a Cloud-Based Computing Collaboration among Construction Stakeholders
The uniqueness of the construction industry can be understood in the large volumes of information in terms of paper works, processes, and communication disseminated
daily. The voluminous information requires close coordination which cloud based systems offer. The aim of this research is to assess the linkages and leakages in a
cloud-based computing collaboration among construction stakeholders. A purposive sampling technique was used in selecting the participants of the study. A questionnaire based instrument was distributed to eighty (80) construction
stakeholder in Lagos State, Nigeria. The data collected was analyzed using SPSS v.21. Statistical tools such as frequencies, stacked bars, mean scores, factor analysis,
and analysis of variance (ANOVA) were used in the study. The result of the study revealed that construction stakeholders rarely utilize cloud-based technologies for their construction processes. Construction professionals that access cloud based technologies, do so with their smart mobile phones, laptops, and tablet. The study classified the leakages that exist in the use of cloud-based technologies as securitybased factors, cloud-based infrastructure factors, and cloud-based benefits deficiency based factors. In conclusion, the study revealed that the linkages in the use of cloudbased technologies include knowledge sharing, remote access of back-office activities and engendering collaboration among construction stakeholders. It was recommended that construction stakeholders should leverage on the benefits cloud-based technologies has to offer in today’s competitive economy. Construction stakeholdersshould be adequately informed on the available cloud-based computing technologies and the additions it can bring into the construction process. Cloud computing technology vendors should improve on the security and privacy features of the platform for adequate protection of building data
Jahn-Teller polarons and their superconductivity in a molecular conductor
We present a theoretical study of a possibility of superconductivity in a
three dimensional molecular conductor in which the interaction between
electrons in doubly degenerate molecular orbitals and an {\em intra}molecular
vibration mode is large enough to lead to the formation of
Jahn-Teller small polarons. We argue that the effective polaron-polaron
interaction can be attractive for material parameters realizable in molecular
conductors. This interaction is the source of superconductivity in our model.
On analyzing superconducting instability in the weak and strong coupling
regimes of this attractive interaction, we find that superconducting transition
temperatures up to 100 K are achievable in molecular conductors within this
mechanism. We also find, for two particles per molecular site, a novel Mott
insulating state in which a polaron singlet occupies one of the doubly
degenerate orbitals on each site. Relevance of this study in the search for new
molecular superconductors is pointed out.Comment: Submitted to Phys. Rev.
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