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- Hedin, Lars, et al.
(författare)
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Effects of Electron-Electron and Electron-Phonon Interactions on the One-Electron States of Solids
- 1969
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Ingår i: Solid State Physics. - 9780126077230 ; 23, s. 1-181
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Bokkapitel (refereegranskat)abstract
- Publisher Summary: This chapter discusses two major developments that have taken place over the past decade. First is the enormous wealth of energy band calculations that have had tremendous success in explaining the properties of specific solids, but in which the connection with first principles is not always apparent. Second is the spectacular progress of many-body theory applied to the solid state that has given a number of new results, although often of a rather general and formal nature, such as to provide the justification and a formal basis for a one-electron theory. The electron gas problem is treated in some detail here. The problem of the crystal potential is given due attention. It discusses the potential from the ion cores as well as from the valence electrons, and suggests schemes that incorporate essential exchange and correlation effects for the valence electrons. An energy band calculation that properly includes the effects of exchange and correlation describes the elementary excitations called quasi particles. Quasi-particle properties are usually discussed using the remarkable Landau theory of the Fermi liquid. This chapter gives a brief presentation of the theory and reviews the present status of calculations of the Fermi liquid parameters and how they are determined from experiments.
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- Hedin, Lars
(författare)
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Many-body effects in soft X-ray emission in metals
- 1967
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Ingår i: Solid State Communications. - : Elsevier BV. - 1879-2766 .- 0038-1098. ; 5:6, s. 451-454
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Tidskriftsartikel (refereegranskat)abstract
- Soft X-ray emission in metals is treated, taking many-body effects and the electron-hole attraction into account. An appropriate connection with electron gas results is made. The structure in the low energy tail due to many-body effects are discussed, and the existence of a new critical point is suggested.
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- Hedin, Lars
(författare)
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New Method for Calculating the One-Particle Green's Function with Application to the Electron-Gas Problem
- 1965
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Ingår i: Physical Review series I. - 0031-899X. ; 139:3A, s. 796-823
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Tidskriftsartikel (refereegranskat)abstract
- A set of successively more accurate self-consistent equations for the one-electron Green's function have been derived. They correspond to an expansion in a screened potential rather than the bare Coulomb potential. The first equation is adequate for many purposes. Each equation follows from the demand that a corresponding expression for the total energy be stationary with respect to variations in the Green's function. The main information to be obtained, besides the total energy, is one-particle-like excitation spectra, i.e., spectra characterized by the quantum numbers of a single particle. This includes the low-excitation spectra in metals as well as configurations in atoms, molecules, and solids with one electron outside or one electron missing from a closed-shell structure. In the latter cases we obtain an approximate description by a modified Hartree-Fock equation involving a "Coulomb hole" and a static screened potential in the exchange term. As an example, spectra of some atoms are discussed. To investigate the convergence of successive approximations for the Green's function, extensive calculations have been made for the electron gas at a range of metallic densities. The results are expressed in terms of quasiparticle energies E(k) and quasiparticle interactions f(k, k′). The very first approximation gives a good value for the magnitude of E(k). To estimate the derivative of E(k) we need both the first- and the second-order terms. The derivative, and thus the specific heat, is found to differ from the free-particle value by only a few percent. Our correction to the specific heat keeps the same sign down to the lowest alkali-metal densities, and is smaller than those obtained recently by Silverstein and by Rice. Our results for the paramagnetic susceptibility are unreliable in the alkali-metal-density region owing to poor convergence of the expansion for f. Besides the proof of a modified Luttinger-Ward-Klein variational principle and a related self-consistency idea, there is not much new in principle in this paper. The emphasis is on the development of a numerically manageable approximation scheme.
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- Hedin, Lars, et al.
(författare)
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New structure in the single-particle spectrum of an electron gas
- 1967
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Ingår i: Solid State Communications. - : Elsevier BV. - 1879-2766 .- 0038-1098. ; 5:4, s. 237-239
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Tidskriftsartikel (refereegranskat)abstract
- Calculations of the one-electron Green's function give a single-particle spectrum where, besides the usual quasi-particles, a new peak of appreciable strength appears which corresponds to an electron coupled to real plasmons.
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- Hedin, Lars, et al.
(författare)
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On the single-particle spectrum of an interacting electron gas
- 1967
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Ingår i: [Host publication title missing]. - : Wiley. ; 1, s. 237-237
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Konferensbidrag (refereegranskat)abstract
- n the many-body theory of conduction electrons in a metal the single-particle spectrum is described not simply by the energy versus momentum relation as in band theory but by a function that describes the actual shape of the spectrum for a given momentum and has an appreciable spread in energy. Calculations of the spectral strength function for electrons in a uniform electron gas are described, where, besides the usual quasi-particle peak and a broad background, a new peak of appreciable strength appears for small momenta. The new excitation corresponds to a coupled mode of an electron and real plasmons. It has a strong effect on the energy distribution of electrons in the system. The effects should show up only in certain types of experiments that depend on the energy spectrum in the region where the new mode occurs.
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- Rosander, T., et al.
(författare)
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Thermal conductivity of Bi to 40 KBAR
- 1969
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Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 29:9, s. 517-518
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity of polycrystalline Bi was determined in cylindrical geometry through three solid phases at 300°K. The thermal and electrical conductivities are compared.
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