Spin waves and electronic interactions in La2CuO4

The magnetic excitations of the square-lattice spin-1/2 antiferromagnet and high- T(c) parent compound La2CuO4 are determined using high-resolution inelastic neutron scattering. Sharp spin waves with absolute intensities in agreement with theory including quantum corrections are found throughout the Brillouin zone. The observed dispersion relation shows evidence for substantial interactions beyond the nearest-neighbor Heisenberg term which can be understood in terms of a cyclic or ring exchange due to the strong hybridization path around the Cu4O4 square plaquettes.     

Coulomb interactions in metallic VO2

The intra-cationic coulomb energy in the metallic phase of VO₂ is estimated using a model in which the observed spin susceptibility and its temperature dependence arise from correlation modified exchange enhancement of the spin susceptibility of the d - subbands.     

Impurity induced interactions in diluted La2CuO4

A non-magnetic impurity, such as Zn, doped into a non-frustrated antiferromagnet can induce substantial frustrating interactions among the spins surrounding it and result in an enhanced suppression of the antiferromagnetic order. In addition, the strength of the intra-plane exchange couplings surrounding impurities is reduced by the lattice distortions. Using quantum Monte Carlo, we calculate the initial suppression rate of the staggered magnetization in a two-dimensional diluted Heisenberg antiferromagnet with both frustrating interaction and lattice distortion induced by the impurity. We find that the lattice distortion alone cannot explain the experimental results, while the dominant effect of enhanced order suppression is due to the frustrating interaction.     

Coulomb potentials in heavy-ion interactions

The usual point charge approximation for the Coulomb potential in heavy-ion interactions is compared with more realistic treatments. Elastic scattering and transfer reaction calculations appear to be insensitive to the form of the Coulomb potential used.     

Magnetic ground state of coupled edge-sharing CuO2 spin chains

By means of density functional theory, we investigate the magnetic ground state of edge-sharing CuO2 spin chains, as found in the (La,Ca,Sr)14Cu24O41 system, for instance. Our data rely on spin-polarized electronic structure calculations including on-site interaction [local density approximation plus the multiorbital mean-field Hubbard model (LDA+U)] and an effective model for the interchain coupling. Strong doping dependence of the magnetic order is characteristic for edge-sharing CuO2 spin chains. We determine the ground state magnetic structure as function of the spin-chain filling and quantify the competing exchange interactions.     

Strong Coulomb effects in hole-doped Heisenberg chains

Substances such as the “telephone number compound” Sr₁₄Cu₂₄O₄₁ are intrinsically hole-doped. The involved interplay of spin and charge dynamics is a challenge for theory. In this article we propose to describe hole-doped Heisenberg spin rings by means of complete numerical diagonalization of a Heisenberg Hamiltonian that depends parametrically on hole positions and includes the screened Coulomb interaction among the holes. It is demonstrated that key observables like magnetic susceptibility, specific heat, and inelastic neutron scattering cross section depend sensitively on the dielectric constant of the screened Coulomb potential.     

Dual character of the electronic structure of YBa2Cu4O8: the conduction bands of CuO2 planes and CuO chains

We use microprobe angle-resolved photoemission spectroscopy (microARPES) to separately investigate the electronic properties of CuO2 planes and CuO chains in the high temperature superconductor, YBa2Cu4O8. For the CuO2 planes, a two-dimensional (2D) electronic structure is observed and, in contrast to Bi2Sr2CaCu2O8+delta, the bilayer splitting is almost isotropic and 50% larger, which strongly suggests that bilayer splitting has no direct effect on the superconducting properties. In addition, the scattering rate for the bonding band is about 1.5 times stronger than the antibonding band and is independent of momentum. For the CuO chains, the electronic structure is quasi-one-dimensional and consists of a conduction and insulating band. Finally, we find that the conduction electrons are well confined within the planes and chains with a nontrivial hybridization.     

Spinon thermal conductivity of-(CuO2)-spin chains in LiCuVO4

The thermal conductivity κ ^b_tot of the quasi-one-dimensional (S=1/2) Heisenberg antiferromagnet LiCuVO₄ with uniform (-CuO₆-) spin chains aligned parallel to the b axis in a crystal with an orthorhombically distorted inverse spinel structure is measured in the temperature range 10–300 K. The spinon component κ ^chain_m of the thermal conductivity is separated out.

     

Coulomb interactions and nanoscale electronic inhomogeneities in manganites

We study electronic inhomogeneities in manganites using simulations on a microscopic model with Coulomb interactions amongst two electronic fluids-one localized (polaronic), the other extended-and dopant ions. The long range Coulomb interactions frustrate phase separation induced by the large on site repulsion between the fluids. A single phase ensues which is inhomogeneous at a nanoscale, but homogeneous on mesoscales, with many features that agree with experiments. This, we argue, is the origin of nanoscale inhomogeneities in manganites, rather than phase competition or disorder effects.     

Crossover behavior in fluids with Coulomb interactions

According to extensive experimental findings, the Ginzburg temperature t_G for ionic fluids differs substantially from that of nonionic fluids [W. Schr?er, H. Weig?rtner, Pure Appl. Chem. 76, 19 (2004)]. A theoretical investigation of this outcome is proposed here by a mean field analysis of the interplay of short and long range interactions on the value of t_G. We consider a quite general continuous charge-asymmetric model made of charged hard spheres with additional short-range interactions (without electrostatic interactions the model belongs to the same universality class as the 3D Ising model). The effective Landau-Ginzburg Hamiltonian of the full system near its gas-liquid critical point is derived from which the Ginzburg temperature is calculated as a function of the ionicity. The results obtained in this way for t_G are in good qualitative and sufficient quantitative agreement with available experimental data.     

Coulomb and strong interactions for Bose-Einstein correlations

We present an analytical formula for the Bose-Einstein correlations (BEC) which includes effects of both Coulomb and strong final state interactions (FSI). It was obtained by using Coulomb wave function together with the scattering partial wave amplitude of the strong interactions describing data on thes-wave phase shift. We have proved numerically that this method is equivalent to solving Schrödinger equation with Coulomb and thes-wave strong interaction potentials. As an application we have analysed, using our formula which includes the degree of coherence and the long range correlation, the data fore ⁺ e ^? annihilations. We have found that the degree of coherence present in our formula approaches approximately unity whereas the long range correlation parameter becomes approximately zero. These results suggest that the physical meanings of the fractional degree of coherence and the long range correlation observed in various other analyses can most probably be attributed to FSI.     

Erratum to: Effects of Coulomb interactions and disorder in triple-Weyl semimetals

The European Physical Journal B - Intrinsic and Rashba spin–orbit interactions in strained graphene is studied within the tight-binding (TB) approach. Dependence of Slater–Koster (SK)...