Thes-f model with Coulomb repulsion: Thermodynamics of two atomic cluster. Spin 1/2

1982 ◽  
Vol 45 (4) ◽  
pp. 331-337 ◽  
Author(s):  
M. Matlak ◽  
A. Ramakanth ◽  
K. Skrobiś
Author(s):  
P. Fraundorf ◽  
J. Tentschert

Since the discovery of their etchability in the early 1960‘s, nuclear particle tracks in insulators have had a diverse and exciting history of application to problems ranging from the selective filtration of cancer cells from blood to the detection of 244Pu in the early solar system. Their usefulness stems from the fact that they are comprised of a very thin (e.g. 20-40Å) damage core which etches more rapidly than does the bulk material. In fact, because in many insulators tracks are subject to radiolysis damage (beam annealing) in the transmission electron microscope, the body of knowledge concerning etched tracks far outweighs that associated with latent (unetched) tracks in the transmission electron microscope.With the development of scanned probe microscopies with lateral resolutions on the near atomic scale, a closer look at the structure of unetched nuclear particle tracks, particularly at their point of interface with solid surfaces, is now warranted and we think possible. The ion explosion spike model of track formation, described loosely, suggests that a burst of ionization along the path of a charged particle in an insulator creates an electrostatically unstable array of adjacent ions which eject one another by Coulomb repulsion from substitutional into interstitial sites. Regardless of the mechanism, the ejection process which acts to displace atoms along the track core seems likely to operate at track entry and exit surfaces, with the added feature of mass loss at those surfaces as well. In other words, we predict pits whose size is comparable to the track core width.


2020 ◽  
Vol 2 (3) ◽  
Author(s):  
Andreas Sinner ◽  
Yurii E. Lozovik ◽  
Klaus Ziegler

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Matthew J. Trott ◽  
Chris A. Hooley

AbstractThe transition metal dichalcogenides offer significant promise for the tunable realisation and application of correlated electronic phases. However, tuning their properties requires an understanding of the physical mechanisms underlying their experimentally observed ordered phases, and in particular the extent to which lattice vibrations are a necessary ingredient. Here we present a potential mechanism for charge-density-wave formation in monolayers of vanadium diselenide in which the key role at low energies is played by a combination of electron–electron interactions and nesting. There is a competition between superconducting and density-wave fluctuations as sections of the Fermi surface are tuned to perfect nesting. This competition leads to charge-density-wave order when the effective Heisenberg exchange interaction is comparable to the effective Coulomb repulsion. When all effective interactions are purely repulsive, it results instead in d-wave superconductivity. We discuss the possible role of lattice vibrations in enhancing the effective Heisenberg exchange during the earlier stages of the renormalisation group flow.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Igor N. Karnaukhov

AbstractUsing mean field approach, we provide analytical and numerical solution of the symmetric Anderson lattice for arbitrary dimension at half filling. The symmetric Anderson lattice is equivalent to the Kondo lattice, which makes it possible to study the behavior of an electron liquid in the Kondo lattice. We have shown that, due to hybridization (through an effective field due to localized electrons) of electrons with different spins and momenta $$\mathbf{k} $$ k and $$\mathbf{k} +\overrightarrow{\pi }$$ k + π → , the gap in the electron spectrum opens at half filling. Such hybridization breaks the conservation of the total magnetic momentum of electrons, the spontaneous symmetry is broken. The state of electron liquid is characterized by a large Fermi surface. A gap in the spectrum is calculated depending on the magnitude of the on-site Coulomb repulsion and value of s–d hybridization for the chain, as well as for square and cubic lattices. Anomalous behavior of the heat capacity at low temperatures in the gapped state, which is realized in the symmetric Anderson lattice, was also found.


2016 ◽  
Vol 71 (5) ◽  
pp. 476-481 ◽  
Author(s):  
V. V. Komarov ◽  
A. M. Popova ◽  
L. Schmidt ◽  
H. Jungclas

1965 ◽  
Vol 43 (5) ◽  
pp. 1569-1576 ◽  
Author(s):  
N. Solony ◽  
F. W. Birss ◽  
John B. Greenshields

The semiempirical SCF–LCAO–MO method of Pariser–Parr–Pople is utilized in the study of the π-electronic structures of thiophene, furan, and pyrrole. The core Hamiltonian expansion contains a Uz++ term, the potential due to the ionized hetero-atom contributing two electrons to the π-system. The γzz, one-center coulomb repulsion integral for the hetero-atom is evaluated from the experimental spectroscopic data only. With the resonance integral βczc as the only variable parameter, the calculated π*–π electronic transitions are in a satisfactory agreement with the experimental data.


1999 ◽  
Vol 60 (23) ◽  
pp. 15654-15659 ◽  
Author(s):  
G. Fano ◽  
F. Ortolani ◽  
A. Parola ◽  
L. Ziosi

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
A. Pustogow ◽  
R. Rösslhuber ◽  
Y. Tan ◽  
E. Uykur ◽  
A. Böhme ◽  
...  

AbstractCoulomb repulsion among conduction electrons in solids hinders their motion and leads to a rise in resistivity. A regime of electronic phase separation is expected at the first-order phase transition between a correlated metal and a paramagnetic Mott insulator, but remains unexplored experimentally as well as theoretically nearby T = 0. We approach this issue by assessing the complex permittivity via dielectric spectroscopy, which provides vivid mapping of the Mott transition and deep insight into its microscopic nature. Our experiments utilizing both physical pressure and chemical substitution consistently reveal a strong enhancement of the quasi-static dielectric constant ε1 when correlations are tuned through the critical value. All experimental trends are captured by dynamical mean-field theory of the single-band Hubbard model supplemented by percolation theory. Our findings suggest a similar ’dielectric catastrophe’ in many other correlated materials and explain previous observations that were assigned to multiferroicity or ferroelectricity.


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