81 research outputs found
Effect of hybridization on the magnetic properties of correlated two-band metals
The magnetic properties of transition-like metals are discussed within the
single site approximation, which is a picture to take into account electron
correlations. The metal is described by two hybridized bands one of which
includes Coulomb correlation. The presented results indicate that
ferromagnetism arises for adequate values of hybridization (V), correlation (U)
and occupation number(). Some similarities with Dynamical
Mean-Field Theory (DMFT) are indicated.Comment: 3 pages, 3 figures, presented at the 53rd MMM08 conference in Austin,
200
Ferromagnetism in two band metals: Combined effect of Coulomb correlation, hybridization and band widths
We study the possibility of ferromagnetism in metals. The metal is described
by two hybridized bands one of which includes Hubbard correlation whereas the
other is uncorrelated. We parametrize the ratio of the band widths and their
centers as well. The original Hamiltonian is transformed in an effective and
simpler one. Only one site retains the full correlation (U) while in the others
acts as an internal field, the self-energy, in the framework of an alloy
analogy approximation. This field, in turn, is self-consistently determined by
imposing the translational invariance of the problem. For several total
electronic occupation numbers (n_{total}) we compare the spin dependent free
energies with the corresponding paramagnetic ones. We present several results
pointing out the mechanism by which the self-consistency introduces a sort of
constraints, for given values of band width and band shift .Comment: 6 pages, 7 figure
Pseudogap and the specific heat of high superconductors
The specific heat of a two dimensional repulsive Hubbard model with local
interaction is investigated. We use the two-pole approximation which exhibits
explicitly important correlations that are sources of the pseudogap anomaly.
The interplay between the specific heat and the pseudogap is the main focus of
the present work. Our self consistent numerical results show that above the
occupation , the specific heat starts to decrease due to the
presence of a pseudogap in the density of states. We have also observed a two
peak structure in the specific heat. Such structure is robust with respect to
the Coulomb interaction but it is significantly affected by the occupation
. A detailed study of the two peak structure is carried out in terms of
the renormalized quasi-particle bands. The role of the second nearest neighbor
hopping on the specific heat behavior and on the pseudogap, is extensively
discussed.Comment: 6 pages, 6 figures, accepted for publication in Solid State
Communication
Specific heat of a non-local attractive Hubbard model
The specific heat of an attractive (interaction ) non-local Hubbard
model is investigated. We use a two-pole approximation which leads to a set of
correlation functions. In particular, the correlation function $\
G\delta\delta=1-n_Tn_T=n_{\uparrow}+n_{\downarrow}(0,\pm\pi)(\pm\pi,0)$ eliminates the two peak structure, the low
temperature peak remaining. The effects of the second nearest neighbor hopping
on the specific heat are also investigated.Comment: 5 pages, 7 figure
On the use of a single site approximation to describe correlation in pure metals
The magnetic properties of pure transition-like metals are discussed within
the single site approximation, to take into account the electron correlation.
The metal is described by two hybridized bands one of which includes the
Coulomb correlation. Our results indicate that ferromagnetism follows from
adequate values of the correlation and hybridization.Comment: 2 pages and 2 figure
- …