Search for dissertations about: "phonon"

Showing result 21 - 25 of 172 swedish dissertations containing the word phonon.

  2. 21. Microscopic Mechanisms of the Formation, Relaxation and Recombination of Excitons in Two-Dimensional Semiconductors

    Author : Samuel Brem; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; relaxation dynamics; 2D materials; density matrix formalism; excitons; exciton-phonon interaction; Bloch equations;

    Abstract : Monolayers of Transition Metal Dichalcogenides (TMDs) present a giant leap forward towards the realization of semiconductor devices with atomic scale thickness. As a natural consequence of their two-dimensional character TMDs exhibit a reduced dielectric screening, leading to the formation of unusually stable excitons, i.e. READ MORE

  4. 22. Monte Carlo simulation of electron transport in semiconducting zigzag carbon nanotubes

    Author : Kannan Thiagarajan; Ulf Lindefelt; Hans-Erik Nilsson; Michele Goano; Mittuniversitetet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Carbon nanotubes; Monte Carlo method; drift velocity; mobility; electron-phonon scattering; and electron-defect scattering.;

    Abstract : Since the advent of nanoscale material based electronic devices, there has been a considerable interest in exploring carbon nanotubes from fundamental science and technological perspectives. In carbon nanotubes, the atoms form a cylindrical structure with a diameter of the order 1nm. READ MORE

  5. 23. Role of charge and spin fluctuations and their interplay in solids : A Green’s function approach

    Author : Tor Sjöstrand; Matematisk fysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Green’s function; correlations; collective excitations; screened interaction; electric polarization; orbital and spin magnetization; magnon-phonon interaction; Fierz ambiguity; time-dependent exchange-correlation potential;

    Abstract : Due to the large number of electrons, solid state physics boils down to many-body approximations in which only selected types of collective excitations are taken into account, guided by the emergent properties of the material under study. In this thesis, the collective excitations of primary interest are electronic charge and spin fluctuations(plasmons and magnons) and nuclear charge fluctuations (phonons). READ MORE

  6. 24. Microscopic Theory of Exciton Dynamics in Two-Dimensional Materials

    Author : Samuel Brem; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; exciton-phonon interaction; van der Waals materials; relaxation dynamics; excitons; 2D materials; density matrix formalism;

    Abstract : Transition Metal Dichalcogenides (TMDs) present a giant leap forward towards the realization of nanometer-sized quantum devices. As a direct consequence of their truly two-dimensional character, TMDs exhibit a strong Coulomb-interaction, leading to the formation of stable electron-hole pairs, so-called excitons. READ MORE

  7. 25. Photo-induced Structural Dynamics in Transition Metal Dichalcogenides

    Author : Shaozheng Ji; Jonas Weissenrieder; James Gardner; Oscar Tjernberg; Fabrizio Carbone; KTH; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; ultrafast electron microscope; coherent shear phonon; photo-induced phase transition; 1T-TaSe2; Td-WTe2; charge density wave; ultrasnabbt elektronmikroskop; koherent skjuvphonon; fotoinducerad fasövergång; 1T-TaSe2; Td-WTe2; laddningsdensitetsvåg; Material and Nano Physics; Material- och nanofysik;

    Abstract : Ultrafast electron microscope (UEM), a combination of transmission electron microscopy and laser-based pump-probe techniques, facilitates ultrafast imaging, diffraction, and electron-spectroscopy with high spatial resolution. The unique advantages of UEM enable local ultrafast dynamic studies in materials, nano-system, and biology. READ MORE