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Electron Interaction (electron + interaction)
Selected AbstractsQuantum phase transition between antiferromagnetic and charge order in the Hubbard,Holstein modelPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2010Johannes Bauer Abstract We explore the quantum phase transitions between two ordered states in the infinite dimensional Hubbard,Holstein model at half filling. Our study is based on the dynamical mean field theory (DMFT) combined with the numerical renormalization group (NRG), which allows us to handle both strong electron,electron and strong electron,phonon interactions. The transition line is characterized by an effective electron,electron interaction. Depending on this effective interaction and the phonon frequency ,0 one finds either a continuous transition or discontinuous transition. Here, the analysis focuses on the behavior of the system when the electron,electron repulsion U and the phonon-mediated attraction , are equal. We first discuss the adiabatic and antiadiabatic limiting cases. For finite ,0 we study the differences between the antiferromagnetic (AFM) and charge order, and find that when present the AFM state has a lower energy on the line. [source] Effect of electron,electron interaction and plasmon excitation on the density-of-states for a two-dimensional electron liquidPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007Godfrey Gumbs Abstract We calculate the Green's function for an interacting two-dimensional electron liquid whose strength of interaction is characterized by the electron density parameter rs. The screened electron,electron interaction is expressed in terms of a frequency and wave vector-dependent dielectric function , (q, w). If this screening is neglected, the tunneling density of states (DOS) is strongly modified by the electron,electron interaction. This modification is seen as a dip near the Fermi energy. This dip becomes deeper and narrower as rs is increased. When screening is included, the DOS is considerably affected by the collective plasma excitations. In particular, the range of frequencies where the plasmon excitations contribute increases with rs. Also, the DOS near the Fermi energy for the screened electron liquid depends on the electron density. We treat , (q, w) in the hydrodynamical approximation in order to investigate the way in which the tunneling DOS is modified at various electron densities. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Interaction effects in high-mobility two-dimensional electron and hole systemsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2005A. K. Savchenko Abstract Electron,electron interaction in the presence of impurities is studied in two-dimensional systems where the parameter kBT,/, changes from 0.1 to 10 (, is the momentum relaxation time). This corresponds to the intermediate and ballistic regimes of electron interaction. We analyse the interaction correction to the Drude conductivity in terms of recent theories and show that it is strongly dependent on the character of the impurity potential. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transport properties of hydrogen-doped (Zr803d20)1,xHx (3d = Co, Ni) metallic glassesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2004I. Kokanovi Abstract The electrical resistivities of hydrogen-doped (Zr803d20)1,xHx (3d = Ni, Co; x , 0.11) metallic glasses have been measured at temperatures between 2 K and 110 K and in magnetic fields up to 1 T for various dopant concentrations. These systems have a high room-temperature resistivity (, > 160 ,, cm) and become superconducting below 4 K. The increase of the room-temperature resistivity and its temperature coefficient with hydrogen dopant concentration is explained as due to an increase of disorder with hydrogen-doping. The temperature and magnetic field dependence of the resistivity has been analysed using theoretical models of weak-localisation and electron,electron interaction in disordered conductors. The hydrogen dopant is found to reduce the effective electron diffusion constant, D, the spin-orbit scattering rate, ,,1so, the superconducting transition temperature, Tc, and broadens the superconducting transition region. The contribution of the Maki-Thompson interaction to the magnetoresistivity is also reduced. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Aharonov,Bohm effect of a quantum ring in the Kondo regimePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003U. F. Keyser Abstract We investigate a small tuneable quantum ring fabricated by direct local oxidation using an atomic force microscope. The device contains very few electrons and is tuned into the Kondo regime. We study this Kondo effect by temperature dependent measurements. At finite bias voltages we observe additional peaks. These vanish with increasing temperature indicating Kondo correlations for these excited states. Additionally, the geometry of our device allows to study Aharonov,Bohm oscillations in the Kondo regime for a device containing less than ten electrons. We observe a modulation of the Kondo effect with a reduced Aharonov,Bohm period explained by electron,electron interaction in our small quantum ring. [source] ,,, Energy Separation in Homodesmotic ReactionsCHEMPHYSCHEM, Issue 12 2005Georg Hohlneicher Dr. Abstract A well-established quantity for specifying the aromaticity or antiaromaticity of cyclic conjugated molecules is the so-called aromatic stabilization energy (ASE), which can be derived,either experimentally or theoretically,from appropriate homodesmotic reactions. To gain further insight into the origin of aromaticity, several schemes have been devised to partition ASE into nuclear and electronic as well as , and , contributions, some of which have resulted in contradictory statements about the driving force of aromatic stabilization. Currently, these contradictions have not been resolved and have resulted in a confusing distinction between two different types of aromaticity: extrinsic and intrinsic aromaticity. By investigating different homodesmotic reactions we show that, in contrast to ASE itself, the individual contributions that enter the ASE can strongly depend on the type of reaction. Caution is therefore advised if conclusions or physical interpretations are derived from the individual components. The contradictions result from the fact that some reactions suffer from an imbalance in the number of interaction terms at the two sides of the reaction equation. The concept of isointeractional reactions is introduced and results in the elimination of the imbalance. For these reactions, the contradictions disappear and the distinction between intrinsic and extrinsic aromaticity becomes unnecessary. As far as the ,,, partitioning is concerned, several schemes proposed in the literature are compared. Contradictory results are obtained depending on the partitioning scheme and reaction used. In this context, it is demonstrated that for the partitioning of the electron,electron interaction, the scheme introduced by Jug and Köster is the one that is most theoretically grounded. [source] Synthesis and crystal structure investigation of pyridine-2-(3,-mercaptopropanoic acid)- N -oxideCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2007R. Ramasubramanian Abstract Pyridine-2-(3,-mercaptopropanoic acid)- N -oxide (I), is a higher homologue of 1-oxopyridinium-2-thioacetic acid (II) [1]. It crystallizes in monoclinic space group P21 with a = 9.2168(2) Å, b = 4.1423(2) Å, c = 11.3904(4) Å, , = 98.65(2)°, V = 429.93(3) Å3 and Z = 2. The least-squares refinement gave residual index R = 0.024 for 1070 observed reflections. The introduction of an additional methylene group in (II) causes a flip in the carboxylic acid group of (I) that facilitates the molecules to align infinite antiparallel chains through strong C,H···O interactions. The molecules are interlinked by O,H···O hydrogen bonding across the chains and forming an infinite screw chain along y-direction. The molecular packing is stabilized by O,H···O and C,H···O hydrogen bonding and ,-, electron interactions. This is an important facet of the crystal packing. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hartree,Fock interactions in the integer quantum Hall effectPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2008Rudolf A. Römer Abstract We report on numerical studies into the interplay of disorder and electron,electron interactions within the integer quantum Hall regime, where the presence of a strong magnetic field and two-dimensional confinement of the electronic system profoundly affects thermodynamic and transport properties. We emphasise the behaviour of the electronic compressibility, the local density of states, and the Kubo conductivity. Our treatment of the electron,electron interactions relies on the Hartree-Fock approximation so as to achieve system sizes comparable to experimental situations. Our results clearly exhibit manifestations of various interaction-mediated features, such as non-linear screening, local charging, and g -factor enhancement, implying the inadequacy of independent-particle models for comparison with experimental results. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||