Self-energy contributions to the dynamic structure factor of an electron liquid

It is demonstrated that the experimentally observed two-peak structure in the dynamic structure factor of an electron liquid cannot be explained by the finite life-times of the quasiparticles in the way proposed by Mukhopadhyay et al. The two-peak structure obtained by them disappears if the frequency dependence of the one-particle self-energy is taken into account.     

On the dynamic form factor of an electron liquid

The mean field theories of an electron liquid at metallic densities, which go beyond the RPA, and which have been fairly successful so far, are shown to be inadequate when tested against phenomena involving high frequencies. It is also shown that by making a simple Gaussian ansatz for the imaginery part of the response function, χ″(q,ω), and using the zeroth, the first and the third frequency moments of density spectral function to determine the unknown parameters in χ″(q,ω), it is possible to understand at least semiquantitatively the available experimental information regarding the dynamic form factor. Implications of the present analysis as regards the further refinement of the present theories are indicated.     

On the dynamic structure factor for the electron gas

In this paper the well-known electron gas model is expressed as a path integral, and then its dynamic structure factor (DSF) is studied systematically. The study shows that q_c defined in the random phase approximation (RPA) not only is the threshold for a bare plasmon, but also in general is the threshold for any number of renormalized plasmons. The paper focuses on the large momentum transfer case (q > q_c). The conclusion that the self-energy correction appearing in the pertinent Green functions of the DSF vanishes has been reached. An explanation for the first peak in DSF observed in experiments, namely the strong correlation between the single-pair and multi-pair excitations involving only a few pairs, is suggested. An approximate, but nevertheless closed, formula for adding up a set of screened ladder diagrams, which describe the strongest correlation between the single pair and a few (two) pairs, is presented.     

Comments on the presence of a peak in the static structure factor of an electron liquid

Emphasis is laid on the fact that the peak in the static structure factor S(k) observed in a recent experiment at k≈2k_F for conduction electrons in beryllium agrees well with the one predicted by us theoretically some time back. The error in the calculation of the pair correlation function g(r) using the experimental data on S(k) is pointed out. The position of the peak obtained in our g(r) clearly indicates that the effect of electron correlation is to condense into a Wigner lattice at a distance equal to the average interparticle separation rather than making a Mott type transition to an atomic-like state.     

Collective modes and dynamic structure factor of a two-dimensional electron fluid

The electrons bound to the surface of liquid dielectrics by image forces are described as a two-dimensional, classical, one-component plasma with inverse distance interactions. Exact expressions for the collective modes and the dynamic structure factor are obtained from first principles in the limit of long wavelengths. The differences and analogies with uncharged particle fluids and with the three-dimensional one-component plasma are explicitly displayed. The previously used mean-field approximation is shown not to describe weakly coupled systems and to be inadequate in the long-wavelength region.     

On the electron band structure of liquid metals

The electronic structure and the density of states of simple liquid metals is discussed on the basis of a nonlocal and energy-dependent pseudopotential of the Phillips-Kleinman type. As an example we treat lithium. To calculate this pseudopotential we need to know the states and the eigenvalues of the liquid metal ion cores. For these quantities we use: first, the core data of the free atom; second, of the free ion; third, the data we have determined from the measured phonon dispersion curves. The deviations between the band structures, the density of states as calculated with these pseudopotentials and those of free electrons are considerable.     

Spin mass of an electron liquid

We show that in order to calculate correctly the spin current carried by a quasiparticle in an electron liquid one must use an effective "spin mass" m(s) that is larger than both the band mass m(b), which determines the charge current, and the quasiparticle effective mass m(*), which determines the heat capacity. We present two independent estimates of the spin mass enhancement, m(s)/m(b), in two- and three-dimensional electron liquids, based on (i) previously calculated values of the Landau parameters and (ii) a recent theory of the dynamical local field factor in the spin channel. Both methods yield a significant spin mass enhancement, which is larger in two dimensions than in three.     

Dynamical structure factor of the homogeneous electron liquid: its accurate shape and the interpretation of experiments on aluminum

Based on a highly self-consistent theory maintaining the exact functional relations between the self-energy and the vertex part, we evaluate the dynamical structure factor S(q,omega) of the electron liquid. We find striking deviations from S(q,omega) in the random-phase approximation (RPA) for /q/>p(F); besides a broad peak in the one-pair excitation region as seen in the RPA, a clear shoulder appears along a steepened slope at low omega due to electron-hole multiple scattering, and a flattened structure follows due to inseparable interference between one-pair and multipair excitations. Our result agrees with experiments on Al on the whole. The remaining discrepancy is ascribed to the band-structure-induced effect.     

Small and large wave vector behavior for the structure factor of an interacting nonuniform electron gas

We show that the structure factir of an interacting nonuniform electron gas does not go to zero at small q, as one might conclude from the conservation of particles sum rule, and is not given rigorously in the local density approximation at large q.     

An x-radioscopic analysis of the electron structure in molybdenum-rhenium alloys

The Lβ ₂-bands of molybdenum in molybdenum-rhenium alloys are analyzed in this study. On the basis of the authors' own research and on the basis of data found in the technical literature, the changes are analyzed which occur in the electron structure of molybdenum when the latter is alloyed with rhenium. As the rhenium content is increased, the parameters of the electron structure as well as the heat of hydrogen (interstitial impurity) dissolution and the lattice parameter appear to change in distinct stages. The nature of this pattern of changes in stages is discussed.     

Low angle structure factor of liquid aluminium in the mean density approximation

The low angle structure factor of liquid Al is calculated in the mean density approximation. It agrees with the recently observed data of Waseda out to k≈0.4 Å^?1.     

An investigation of the local structure and dynamic properties of undercooled liquid silicon using the orbital-free ab-initio molecular dynamics method

We present results for the static and dynamic structural properties of undercooled liquid Si, at several temperatures between 1550 K and 1100 K, obtained through orbital-free ab-initio molecular dynamics simulations. The local bond angle distributions show a modest increase in the tetrahedral order upon decreasing the temperature. We also analyze the variation of several dynamic magnitudes and transport properties with temperature, showing a tendency to sustain shear waves for some wavevectors as undercooling is deepened. We compare our orbital-free ab-initio results with the limited experimental data available, as well as with results of other ab-initio simulations.     

Bound states of an electron in an impurity potential on the surface of liquid helium

The energies and widths of the levels of an electron on impurity centers on the surface of liquid helium are calculated with allowance for the deformation of the surface. The level shift associated with the deformation effects is small and decreases very slowly with increasing level number. However, even a small shift of the energy levels relative to one another affects ripplon scattering, which makes the main contribution to the level width at low temperatures. It is predicted theoretically that this width depends very strongly on the external parameters and on the level number and that a maximum obtains at a clamping field E _⊥=51500 V/cm. The width of the levels of an electron in a bound state is found to be less than for free electrons. This makes it possible to perform a beautiful spectroscopic experiment. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 599–604 (10 November 1997)