Sökning: "GW-approximation"

Visar resultat 6 - 10 av 10 avhandlingar innehållade ordet GW-approximation.

  1. 6. Periodized Thermal Greens Functions and Applications

    Författare :Andro Sabashvili; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; condensed matter physics; Greens function; graphene; DMFT; RPA; GW;

    Sammanfattning : This work describes a new formalism for Fermionic thermal Greens functions that are discretized in imaginary time. The discretization makes the thermal Greens function periodic in imaginary (Matsubara) frequency space and requires a generalisation of the Dyson equation and Luttinger-Ward-Baym-Kadanoff functional. LÄS MER

  3. 7. Quantitative Modeling of Gain in Quantum Cascade Lasers under Operational Intensities

    Författare :David Winge; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; non-linear response; quantum cascade lasers; modelling; Non-equilibrium Green s functions; Gain clamping; Fysicumarkivet A:2016:Winge; kvantkaskadlaser; terahertz; infrarött; Halvledarfysik; spektroskopi; simulering;

    Sammanfattning : This thesis adresses modeling of quantum cascade lasers using non-equilibrium Green’s functions. Focus lies on the quantitative modeling of the gain when the systems are exposed to strong laser fields, as under realistic opertional conditions. LÄS MER

  4. 8. Complex Excitations in Advanced Functional Materials

    Författare :Johann Lüder; Barbara Brena; Frank de Groot; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; X-ray Absorption Spectroscopy; Photoelectron Spectroscopy; Adsorption; Phthalocyanines; Biphenylene; Excitons; Functional Materials;

    Sammanfattning : Understanding the fundamental electronic properties of materials is a key step to develop innovations in many fields of technology. For example, this has allowed to design molecular based devices like organic field effect transistors, organic solar cells and molecular switches. LÄS MER

  5. 9. First principles study of oxide semiconductors for solar energy applications

    Författare :Maofeng Dou; Clas Persson; Huda Muhammad N.; Sergey Simak; Anna Delin; Peter Johansson; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; photocatalysis; water splitting; oxynitrides; dielectric function; first-principles calculation; density functional theory; electronic structures; Casimir interaction; Teknisk materialvetenskap; Materials Science and Engineering;

    Sammanfattning : The objectives of this thesis are to understand the electronic structures of oxides and oxynitrides for photocatalytic water splitting, examine the Casimir interaction between oxides, and explore possible approach to bridge the Casimir force and material properties for advanced material research. The studies were performed in the framework of the density functional theory, many-body perturbation theory, i. LÄS MER

  7. 10. Optical and Electronic Properties of WO3 and Zn Chalcogenides Alloys: A Theoretical study

    Författare :Gustavo Baldissera; Clas Persson; Naoto Umezawa; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Material and Nano Physics; Material- och nanofysik;

    Sammanfattning : I denna avhandling analyseras optiska och elektroniska egenskaper hos WO3 och Zn-relaterade legeringar med hjälp av täthetsfunktionalteori (DFT). Metoder som går utöver DFT, såsom GW-approximationen och hybridfunktionaler, används för att minimera det fel som genereras av det smala bandgapet som erhålls med konventionella DFT-funktionaler. LÄS MER