Sökning: "random-phase approximation"

Visar resultat 1 - 5 av 21 avhandlingar innehållade orden random-phase approximation.

  1. 1. Computing attosecond delays in atomic photoionisation : A non-iterative method for many-electron correlation within the Random Phase Approximation with Exchange

    Författare :Anton Ljungdahl; Eva Lindroth; Jon Grumer; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Random phase approximation with exchange; attosecond physics; attosecond delays; teoretisk fysik; Theoretical Physics;

    Sammanfattning : När en atom absorberar fotoner, i växelverkan med tillräckligt högenergetisktljus, så kan en (eller flera) av atomens elektroner ”sparkas ut”. Det resulterar i en positivt laddad jon och en (eller flera) så kallade fotoelektroner. Den här processen är känd som den fotoelektriska effekten, men kallas också för fotojonisering. LÄS MER

  3. 2. Unifying first-principles and model approaches for strongly correlated materials : Interplay between long- and short-range correlations

    Författare :Fredrik Nilsson; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; first-principle methods; strongly correlated materials; GW approximation; cRPA; random-phase approximation; dynamical mean-field theory; GW DMFT; downfolding;

    Sammanfattning : In materials with open 3$d$ and 4$f$ shells the valence electrons are relatively localized around the atoms which leads to large electron-electron correlations. These, so called strongly correlated materials, exhibit many intriguing properties such as high $T_c$ superconductivity, colossal magneto-resistance and heavy fermion behaviour. LÄS MER

  4. 3. Plasmons in Nanostructured Graphene

    Författare :Tobias Wenger; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; linear response theory; surface plasmon-polaritons; Plasmons; surface electrodynamics; plasmonics; graphene; random phase approximation;

    Sammanfattning : Plasmons, collective electron density oscillations, provide physicists with intriguing challenges and possibilities. The inherent many-body properties of the plasmons together with their ability to localize light into small volumes make the plasmons interesting from both a purely theoretical viewpoint and an applications point of view. LÄS MER

  5. 4. First principles methods for electronic structure calculations of solids

    Författare :Martin Springer; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; screened interaction; T-matrix; vertex function; GW approximation; Green function; density functional theory; gradient expansion; order N method; Physics; Fysik;

    Sammanfattning : A straightforward gradient expansion of the exchange energy of a perturbed electron gas is performed. Studied perturbations range from very weak to those that produce, e.g., a silicon-like band structure with a band gap. LÄS MER

  7. 5. Calculations on the possibilities for photoionization-delay studies with circularly polarized light

    Författare :Johanna Sörngård; Eva Lindroth; Markus Kowalewski; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Attosecond physics; photoionization delay; circular polarization; Theoretical Physics; teoretisk fysik;

    Sammanfattning : Advances in experimental physics, specifically light sources emitting at an attosecond time scale, has enabled the time resolution of atomic processes like photoionization. Recent developments have allowed these sources to produce light with non-linear polarization. LÄS MER