112 research outputs found
An extended Falicov-Kimball model on a triangular lattice
The combined effect of frustration and correlation in electrons is a matter
of considerable interest of late. In this context a Falicov-Kimball model on a
triangular lattice with two localized states, relevant for certain correlated
systems, is considered. Making use of the local symmetries of the model, our
numerical study reveals a number of orbital ordered ground states, tuned by the
small changes in parameters while quantum fluctuations between the localized
and extended states produce homogeneous mixed valence. The inversion symmetry
of the Hamiltonian is broken by most of these ordered states leading to
orbitally driven ferroelectricity. We demonstrate that there is no spontaneous
symmetry breaking when the ground state is inhomogeneous. The study could be
relevant for frustrated systems like , (in its low temperature
C2/m phase) where two Mott localized states couple to a conduction band.Comment: 6 pages, 8 figure
Metal-Insulator Transition and Band Magnetism in the Spin- Falicov-Kimball Model on A Triangular Lattice with External Magnetic Field
Ground state properties of the spin Falicov-Kimball model on a
triangular lattice in the presence of uniform external magnetic field are
explored. Both the orbital and the Zeeman field-induced effects are taken into
account and in each unit cell only rational flux fractions are considered.
Numerical results, obtained with the help of Monte Carlo simulation algorithm,
reveal that the ground state properties strongly depend on the onsite Coulomb
correlation between itinerant and localized electrons, orbital magnetic field
as well as the Zeeman splitting. Strikingly, for the on-site Coulomb
correlation , the Zeeman splitting produces a phase transition
from paramagnetic metal/insulator to ferromagnetic insulator/metal transition
in the itinerant electron subsystem accompanied by the phase segregation to the
bounded/regular phase in the localized electrons subsystem. For the onsite
Coulomb correlation , although no metal to insulator transition
is observed but a magnetic phase transition from paramagnetic phase to
ferromagnetic phase in the itinerant electron subsystem is observed with the
Zeeman splitting. These results are applicable to the layered systems e.g.
cobaltates, rare earth and transition metal dichalcogenides, ,
, and etc. It has been also proposed
that the results can be realized in the optical lattices with mixtures of light
atoms and heavy atoms using the cold atomic techniques.Comment: 23 pages, 13 figure
Study of ground state phases for spin-1/2 Falicov-Kimball model on a triangular lattice
The spin-dependent Falicov-Kimball model (FKM) is studied on a triangular
lattice using numerical diagonalization technique and Monte-Carlo simulation
algorithm. Magnetic properties have been explored for different values of
parameters: on-site Coulomb correlation , exchange interaction and
filling of electrons. We have found that the ground state configurations
exhibit long range Ne\`el order, ferromagnetism or a mixture of both as is
varied. The magnetic moments of itinerant () and localized () electrons
are also studied. For the one-fourth filling case we found no magnetic moment
from - and -electrons for less than a critical value.Comment: 6 pages, 8 figure
Mercury or Mercury Free Restorations in Oral Cavity
Amalgam is basically a concoction of metals that has been used as a potent filling material in dentistry for the last 150 years. Amalgam usually consists of silver, mercury, tin and copper. Dental amalgam is a material used to fill cavities of tooth. Over the years, amalgam has become a topic of concern because it contains mercury. Mercury is a naturally occurring metal in the environment. Mercury exists as a liquid in room temperature but when heated, it becomes a gas. Flexibility of amalgam as a filling material is due Mercury. An alloy powder, a compound that is soft in nature when mixed with mercury makes it enough to mix and condense into the tooth. It hardens quickly and offers strong resistance to the forces of biting and chewing. There are studies reported on the safety of amalgam fillings. In 2005, European Union launched a comprehensive mercury strategy to reduce use of mercury. In 2008, countries like Norway and Denmark restricted the use of dental amalgam containing mercury. In 2009, this research was evaluated by U.S. Food and Drug Administration (FDA) and found no rationale to limit the use of amalgam. There are certain restorative materials that are available commercially that are mercury free in nature like Gold, Porcelain, Gallium alloys, Composite resin restoratives etc. They offer many advantages over amalgams containing mercury like: seals the dentin from future decay, reinforces remaining tooth structure, provides smooth and bonded margins, conservative and it blends naturally
Statistical properties and different methods of estimation for extended weighted inverted Rayleigh distribution
Phase transitions in a spinless, extended Falicov-Kimball model on the triangular lattice
A numerical diagonalization technique with canonical Monte-Carlo simulation
algorithm is used to study the phase transitions from low temperature (ordered)
phase to high temperature (disordered) phase of spinless Falicov-Kimball model
on a triangular lattice with correlated hopping (). It is observed
that the low temperature ordered phases (i.e. regular, bounded and segregated)
persist up to a finite critical temperature (). In addition, we observe
that the critical temperature decreases with increasing the correlated hopping
in regular and bounded phases whereas it increases in the segregated phase.
Single and multi peak patterns seen in the temperature dependence of specific
heat () and charge susceptibility () for different values of
parameters like on-site Coulomb correlation strength (), correlated hopping
() and filling of localized electrons () are also discussed.Comment: 6 pages, 5 figure
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