Sökning: "density matrix formalism"

Visar resultat 6 - 10 av 19 avhandlingar innehållade orden density matrix formalism.

1. 6. Microscopic modelling of exciton-exciton interactions in atomically thin semiconductors

   Författare :Daniel Erkensten; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; transition-metal dichalcogenides; dark excitons; density matrix formalism; exciton-exciton interactions;

   Sammanfattning : The successful isolation and characterization of the technologically promising material graphene in 2004 has spurred huge interest in other two-dimensional materials. Transition-metal dichalcogenides (TMDs), being one such class of materials, display intriguing properties from both a fundamental and techno- logical point of view. LÄS MER

3. 7. Microscopic Theory of Externally Tunable Exciton Signatures of Two-Dimensional Materials

   Författare :Maja Feierabend; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; localized states; density matrix formalism; magnetic field; transition metal dichalcogenides; Bloch equations; organic inorganic heterostructures; dark excitons; strain;

   Sammanfattning : Atomically thin transition metal dichalcogenides (TMDs) are in the focus of current research due to their efficient light-matter interaction and the remarkably strong Coulomb interaction that leads to tightly bound excitons. Due to their unique band structure, TMDs show a variety of bright and optically inaccessible dark excitonic states. LÄS MER

4. 8. Out of the Dark and into the Light - Microscopic Analysis of Bright, Dark and Trapped Excitons

   Författare :Maja Feierabend; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; density matrix formalism; localized states; impurities; dark excitons; strain; transition metal dichalcogenides; Bloch equations;

   Sammanfattning : Atomically thin transition metal dichalcogenides (TMDs) have been in the focus of current research due to their efficient light-matter interaction, as well as the remarkably strong Coulomb interaction that leads to tightly bound excitons. Due to their unique band structure, TMDs show a variety of optically accessible bright and inaccessible dark excitons. LÄS MER

5. 9. 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. 10. On the Properties of Some Strongly Correlated Systems - Analytical and Numerical Studies

   Författare :Jurij Smakov; KTH; []
   Nyckelord :mean field theory; magnetic multilayers; Curie temperature; compensation temperature; scanning tunneling microscopy; tunneling; superconductivity; local density of states; Josephson effect; tunneling Hamiltonian formalism; impurities in superconducto;

   Sammanfattning : This thesis is dedicated to analytical and numerical studiesof a few models of strongly correlated systems and thedevelopment of techniques for such studies. The common name"strongly correlated" refers to systems in which theinteractions (correlations) between the constituent particleslead to nontrivial properties, such as various types ofmagnetism, superconductivity, and exotic phases. LÄS MER