Home  About us  Contact
 

Strong Electronic Correlations (strong + electronic_correlation)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Forward scattering peak in the electron,phonon interaction and impurity scattering of cuprate superconductors

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2005
M. L. Kuli
Abstract The important role of the electron,phonon interaction (EPI) in explaining the normal state properties and pairing mechanism in high- Tc superconductors (HTSC) is discussed. A number of experiments are analyzed such as: dynamical conductivity, Raman scattering, neutron scattering, ARPES, tunnelling measurements, and etc. They give convincing evidence that the EPI dominantly contributes to pairing in HTSC oxides. Strong electronic correlations cause the forward scattering peak (FSP) in the EPI and in the non-magnetic impurity potential. The theory based on the FSP (whatever is its origin) explains several puzzling experimental results in ARPES and transport: (1) much smaller transport coupling constant than the pairing one (,tr , ,ph); (2) the ARPES non-shift puzzle , where the nodal kink at 70 meV is unshifted in the superconducting state while the anti-nodal one at 40 meV is shifted; (3) d-wave superconductivity due to the EPI; (4) robustness of d-wave pairing in the presence of nonmagnetic impurities; (5) collapse of the elastic scattering rate near the anti-nodal point in the superconducting state; (6) anomalous temperature dependence of the Hall angle in optimally doped HTSC. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ab-initio simulations of materials using VASP: Density-functional theory and beyond

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2008
Jürgen Hafner
Abstract During the past decade, computer simulations based on a quantum-mechanical description of the interactions between electrons and between electrons and atomic nuclei have developed an increasingly important impact on solid-state physics and chemistry and on materials science,promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within density-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calculations and structural optimizations for systems with thousands of atoms and ab initio molecular dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mechanical and dynamical properties, liquids, glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chemical reactions, and catalysis) are reviewed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

Electronic transport through large quantum dots in the Kondo regime

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003
P. Stefa
Abstract Conductance through a large two-level quantum dot is investigated theoretically in the strong coupling regime. In large quantum dots the separation between discrete levels becomes smaller than the level width due to strong hybridization with electrodes. In such circumstances, apart from strong electronic correlations in the quantum dot, the indirect interaction between both the spatial levels comes into play. It takes place in lateral quantum dots, where the spatial level index is not conserved during the hybridization process with electrodes. This interaction shifts the Kondo resonance peak in the density of states out of the Fermi surface and alters its intensity. This feature can be observed in the differential conductance dependence vs. bias voltage. The virtual inter-level mixing is suppressed for temperatures above the Kondo temperature of the system. The results of theoretical predictions are compared with the results of experimental conductance measurements performed on large quantum dots and some non-typical conductance features are clarified. [source]

Unconventional superconductivity and magnetism in Sr2RuO4 and related materials

ANNALEN DER PHYSIK, Issue 3 2004
I. Eremin
Abstract We review the normal and superconducting state properties of the unconventional triplet superconductor Sr2RuO4 with an emphasis on the analysis of the magnetic susceptibility and the role played by strong electronic correlations. In particular, we show that the magnetic activity arises from the itinerant electrons in the Ru d -orbitals and a strong magnetic anisotropy occurs (,+- < ,zz) due to spin-orbit coupling. The latter results mainly from different values of the g -factor for the transverse and longitudinal components of the spin susceptibility (i.e. the matrix elements differ). Most importantly, this anisotropy and the presence of incommensurate antiferromagnetic and ferromagnetic fluctuations have strong consequences for the symmetry of the superconducting order parameter. In particular, reviewing spin fluctuation-induced Cooper-pairing scenario in application to Sr2RuO4 we show how p -wave Cooper-pairing with line nodes between neighboring RuO2 -planes may occur. We also discuss the open issues in Sr2RuO4 like the influence of magnetic and non-magnetic impurities on the superconducting and normal state of Sr2RuO4. It is clear that the physics of triplet superconductivity in Sr2RuO4 is still far from being understood completely and remains to be analyzed more in more detail. It is of interest to apply the theory also to superconductivity in heavy-fermion systems exhibiting spin fluctuations. [source]