Sökning: "magnetic excitons"

Visar resultat 1 - 5 av 14 avhandlingar innehållade orden magnetic excitons.

1. 1. Bose-Einstein Condensation of Magnetic Excitons in Semiconductor Quantum Wells

   Författare :Vitalie Boţan; Lars Nordström; Sveatoslav Moskalenko; Pavlos Lagoudakis; Uppsala universitet; []
   Nyckelord :Physics; Bose-Einstein condensation; magnetic excitons; electron-hole pairs; electron-hole liquid; magnetorotons; magnetoplasmons; superfluidity; Fysik;

   Sammanfattning : In this thesis regimes of quantum degeneracy of electrons and holes in semiconductor quantum wells in a strong magnetic field are studied theoretically. The coherent pairing of electrons and holes results in the formation of Bose-Einstein condensate of magnetic excitons in a single-particle state with wave vector K. LÄS MER

3. 2. Excitons in a high magnetic field

   Författare :Alexandre V. Petrov; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik; Physics; Fysik; fysik; Physics;

   Sammanfattning : The interaction of excitons with each other and with charged impurities has been studied in a high magnetic field when the distance between the Landau levels is greater than the Coulomb unit of energy, in the frame of the model suitable for description of Wannier excitons in semiconductors. The analytical expressions for the pair interaction potential between hydrogenlike excitons in a high magnetic field are derived for the triplet and singlet terms. LÄS MER

4. 3. Formation and Dynamics of Molecular Excitons and their Fingerprints in Nonlinear Optical Spectroscopy

   Författare :Pär Kjellberg; Kemisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; supraledare; magnetisk resonans; spektroskopi; Physical chemistry; Fysikalisk kemi; Photochemistry; Fotokemi; Kondenserade materiens egenskaper:elektronstruktur; magnetiska och optiska ; egenskaper elektriska; supraconductors; magnetic resonance; relaxation; spectroscopy; Fysik; Chemistry; Kemi; Condensed matter:electronic structure; electrical; Physics; Redfield relaxation theory ; Inhomogeneous broadening ; Time-dependent density functional theory ; Conjugated polymers ; Three-pulse photon echo ; Molecular excitons ; magnetic and optical properties; Nonlinear spectroscopy ;

   Sammanfattning : An efficient transfer of energy in molecular systems has proven to be of fundamental importance both in nature and industrial applications. The ability of molecules to work together forming collective excitations, so-called excitons, plays a key role in for example the extraordinary fast energy transfer involved in the first steps of photosynthesis. LÄS MER

5. 4. 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

7. 5. Energy migration and charge formation in conjugated polymers

   Författare :Yuri Zaushitsyn; Kemisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; magnetic resonance; relaxation; spectroscopy; Kondenserade materiens egenskaper:elektronstruktur; egenskaper elektriska; magnetiska och optiska ; supraledare; magnetisk resonans; spektroskopi; supraconductors; magnetic and optical properties; electrical; energy transfer; Physics; Fysik; Condensed matter:electronic structure; transient absorption spectroscopy; conjugated polymer; charge photogeneration;

   Sammanfattning : The main part of the thesis is concerned with charge photogeneration in conjugated polymers. MeLPPP and POMeOPT films were investigated by transient absorption spectroscopy using different excitation photon energies and light intensities with and without an external electric field. LÄS MER