by Wong Wing Hung. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 127-129). / by Wong Wing Hung. / Acknowledgments --- p.v / Abstract --- p.vii / Chapter 1 --- Introduction - Charming simple harmonic oscillator --- p.1 / Chapter 1.1 --- High school physics --- p.1 / Chapter 1.2 --- Quantum mechanics --- p.2 / Chapter 1.3 --- Quantum dissipative systems and harmonic oscillator --- p.3 / Chapter 1.4 --- Electron-phonon interaction --- p.3 / Chapter 2 --- Dissipative two-state system 一 Spin-boson model --- p.5 / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- "An ""isolated"" two-state system" --- p.6 / Chapter 2.3 --- Coupling to the environment --- p.7 / Chapter 2.4 --- Derivation of the spin-boson Hamiltonian for an extended system --- p.8 / Chapter 2.5 --- Path integral result (optional) --- p.9 / Chapter 2.5.1 --- "Ohmic, unbiased case (s =1,E= 0)" --- p.9 / Chapter 2.5.2 --- "Nonohmic, unbiased case (s≠1,E = 0)" --- p.12 / Chapter 2.5.3 --- Biased case (E ≠0) --- p.12 / Chapter 2.6 --- Our scope --- p.13 / Chapter 3 --- Correlated squeezed-state approach --- p.14 / Chapter 3.1 --- Introduction --- p.14 / Chapter 3.2 --- Coherent-state and squeezed-state approach --- p.15 / Chapter 3.3 --- Correlated squeezed-state approach --- p.16 / Chapter 3.4 --- Tunneling system coupled to two identical phonon modes --- p.19 / Chapter 3.5 --- Tunneling system coupled to a dispersionless phonon bath --- p.23 / Chapter 3.6 --- Conclusion --- p.27 / Chapter 4 --- Exact result for a two-state system coupled to a dispersionless boson bath --- p.28 / Chapter 4.1 --- The decoupling transformation --- p.28 / Chapter 4.2 --- Exact diagonalization result --- p.30 / Chapter 5 --- A variational coupled-cluster approach --- p.38 / Chapter 5.1 --- Introduction --- p.38 / Chapter 5.2 --- """Traditional"" coupled-cluster method" --- p.39 / Chapter 5.2.1 --- Zeroth level --- p.40 / Chapter 5.2.2 --- First level --- p.40 / Chapter 5.2.3 --- Second to fourth levels --- p.41 / Chapter 5.3 --- Variational coupled-cluster method --- p.43 / Chapter 5.3.1 --- Zeroth level --- p.44 / Chapter 5.3.2 --- First level --- p.44 / Chapter 5.3.3 --- Second to fourth levels --- p.45 / Chapter 5.4 --- Traditional CCA based on VCCA --- p.46 / Chapter 5.5 --- Numerical results and discussion --- p.47 / Chapter 5.6 --- Conclusion --- p.56 / Chapter 6 --- A two-state system coupled to an ohmic phonon bath ´ؤ a variational coupled-cluster approach --- p.57 / Chapter 6.1 --- A variable displacement transformation --- p.57 / Chapter 6.2 --- The zeroth level --- p.58 / Chapter 6.3 --- The first level --- p.58 / Chapter 6.4 --- The second level --- p.59 / Chapter 6.5 --- The third level --- p.61 / Chapter 6.6 --- Numerical results and discussions --- p.63 / Chapter 6.7 --- Conclusion --- p.66 / Chapter 7 --- Hubbard-Holstein model --- p.67 / Chapter 7.1 --- The Hubbard model --- p.67 / Chapter 7.2 --- The Hubbard-Holstein model --- p.68 / Chapter 8 --- Heat capacity and spin susceptibility of the Hubbard-Holstein model --- p.69 / Chapter 8.1 --- Grand partition function of the model --- p.69 / Chapter 8.1.1 --- Unperturbed grand partition function --- p.70 / Chapter 8.1.2 --- Second-order correction to grand partition function --- p.72 / Chapter 8.1.3 --- Fourth-order correction to grand partition function --- p.74 / Chapter 8.1.4 --- Third-order correction to the grand partition function --- p.75 / Chapter 8.2 --- One- and two-dimensional regular lattices --- p.76 / Chapter 8.2.1 --- Linear chain --- p.76 / Chapter 8.2.2 --- Square lattice --- p.81 / Chapter 8.3 --- Amorphous models --- p.84 / Chapter 8.3.1 --- One-dimensional model --- p.85 / Chapter 8.3.2 --- Two-dimensional model --- p.88 / Chapter 8.4 --- Conclusion --- p.90 / Chapter 9 --- Nuclear spin-lattice relaxation of the Hubbard-Holstein model --- p.92 / Chapter 9.1 --- Formalism --- p.92 / Chapter 9.2 --- One-dimensional systems --- p.100 / Chapter 9.2.1 --- Regular linear chain --- p.100 / Chapter 9.2.2 --- Amorphous linear chain --- p.102 / Chapter 9.3 --- Three-dimensional systems --- p.103 / Chapter 9.3.1 --- Simple cubic lattice --- p.103 / Chapter 9.3.2 --- Three-dimensional amorphous structure --- p.104 / Chapter 9.4 --- Conclusion --- p.106 / Chapter A --- Coherent state and squeezed state --- p.107 / Chapter A.1 --- Coherent state --- p.107 / Chapter A.2 --- Single-mode squeezed state --- p.109 / Chapter A.3 --- Generalized multimode squeezing --- p.109 / Chapter B --- Construction of a rotation transformation --- p.110 / Chapter C --- Perturbation series for the grand partition function --- p.114 / Chapter D --- Propagator of simple harmonic oscillator --- p.116 / Chapter E --- Derivation of the nuclear spin-lattice relaxation time --- p.118 / Bibliography --- p.127

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Reproduction de : Thèse de doctorat : Physique du solide : Metz : 2008. / Titre provenant de l'écran-titre. Notes bibliographiques. Index.

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Les investigations des effets non-linéaires (NL) qui apparaissent dans les cristaux ferroélectriques deviennent de plus en plus approfondies, et au temps présent, les cristaux optiques NL deviennent de plus en plus utilisés pour le développement de nouvelles sources de radiations cohérente visibles, conversion de fréquences, ainsi que la détection et diverses transformations de signaux et d images. Un cristal très représentatif de cette classe de matériaux est le niobate de lithium, LiNbO3 (LN), qui depuis son apparition n a cessé de surprendre en révélant de plus en plus ses propriétés. Dans ce travail nous montrons comment la microsonde Raman peut être utilisée pour la caractérisation des microstructures de domaines ferroélectriques dans du niobate de lithium périodiquement polarisé (PPLN). L intensité Raman de modes transverses et longitudinaux de phonons optiques a été enregistrée au travers des stries des domaines ferroélectriques à la surface et en volume d échantillons en z-cut , congruents ou dopés, dont l origine provient de différentes techniques de fabrications. Le changement des intensités intégrées à travers ces structures de domaines a été attribué à une influence des contraintes mécaniques et partiellement du champ de dépolarisation écranté. Nous montrons ainsi l importance de la spectroscopie Raman et la place réelle qu elle occupe comme technique de caractérisation. Ceci ouvre la voie à de nombreuses applications dans ce champ d études. / The investigations of the nonlinear (NL) effects that appear in ferroelectric crystals are becoming more and deeper. At the present time, the NL optical crystals are more and more used for the development of new coherent sources of visible radiations, frequency conversion, beside the detection and several signals and images transformations. A very representative crystal of this material class is lithium niobate, LiNbO3 (LN), that since its appearance never stop to surprise with revealing more and more its properties. In this work, we show how Raman microprobe can be used for the characterisation of the ferroelectric domain microstructures in periodically poled lithium niobate (PPLN). The Raman intensity of transverse and longitudinal modes of optical phonons was recorded across the stripe ferroelectric domains at the surface of a z-cut congruent PPLN sample. The change of integrated intensity was attributed to the influence of mechanical stresses and partially screened depolarization fields. So, we show the importance of Raman spectroscopy and the real place that it takes as a characterisation technique. This open the way for numerous applications in this field of studies.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 79-82). Also available in electronic version.

No description available.

Developing materials that can conduct electricity easily, but block the motion of phonons is necessary in the applications of thermoelectric devices, which can generate electricity from temperature differences. In converse, a key requirement as chips get faster is to obtain better ways to dissipate heat. Controlling heat transfer in these crystalline materials devices — such as silicon — is important. The heat is actually the motion or vibration of atoms known as phonons. Finding ways to manipulate the behavior of phonons is crucial for both energy applications and the cooling of integrated circuits. A novel class of artificially periodic structured materials — phononic crystals — might make manipulation of thermal phonons possible. In many fields of physical sciences and engineering, acoustic wave propagation in solids attracts many researchers. Wave propagation phenomena can be analyzed by mathematically solving the acoustic wave equation. However, wave propagation in inhomogeneous media with various geometric structures is too complex to find an exact solution. Hence, the Finite Difference Time Domain method is developed to investigate these complicated problems. In this work, the Finite-Difference Time-Domain formula is derived from acoustic wave equations based on the Taylor’s expansion. The numerical dispersion and stability problems are analyzed. In addition, the convergence conditions of numerical acoustic wave are stated. Based on the periodicity of phononic crystal, the Bloch’s theorem is applied to fulfill the periodic boundary condition of the FDTD method. Then a wide-band input signal is used to excite various acoustic waves with different frequencies. In the beginning of the calculation process, the wave vector is chosen and fixed. By means of recording the displacement field and taking the Fourier transformation, we can obtain the eigenmodes from the resonance peaks of the spectrum and draw the dispersion relation curve of acoustic waves. With the large investment in silicon nanofabrication techniques, this makes tungsten/silicon phononic crystal a particularly attractive platform for manipulating thermal phonons. Phononic crystal makes use of the fundamental properties of waves to create band gap over which there can be no propagation of acoustic waves in the crystal. This crystal can be applied to deterministically manipulate the phonon dispersion curve affected by different crystal structures and to modify the phonon thermal conductivity accordingly. We can expect this unique metamaterial is a promising route to creating unprecedented thermal properties for highly-efficient energy harvesting and thermoelectric cooling.

Thesis (Ph.D.)--Virginia Commonwealth University, 2010. / Prepared for: Dept. of Electrical Engineering. Title from title-page of electronic thesis. Bibliography: leaves 177-185.

Thesis (Ph. D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Electrical Engineering. Title from resource description page. Includes bibliographical references. Unavailable until 6/7/2014.