Thesis advisor: Kevin S. Bedell / The Landau Fermi liquid theory is a very successful theory in condensed matter physics. It provides a phenomenological framework for describing thermodynamics, transport and collective modes of itinerant fermionic systems. In 1957, Silin described the spin waves in polarized Fermi liquids based on Landau Fermi liquid theory, which are related to series of components of the spherical harmonic expansion of the fermi surface. It has been proved by Pomeranchuck that for the Fermi surface to be stable, the Landau parameters should satisfy the relation: $F_l^{s,a}>-(2l+1)$. Whenever the relation is violated, there will exist an instability of the Fermi surface known as a Pomeranchuck instability, such as the Stoner ferromagnetism when $F_0^a→ -1^+$, or phase separation when $F_0^s→ -1^+$. In 1959, Abrikosov and Dzyaloshinskii developed a ferromagnetic Fermi liquid theory(FFLT) of itinerant ferromagnetism based on Landau Fermi liquid theory, whose microscopic foundations were established later by Dzyaloshiskii and Kondratenko. Further studies had been made of this state using a generalized Pomeranchuck instability based on the FFLT of Blagoev, Engelbrecht and Bedell and Bedell and Blagoev. In this thesis, I study a magnetically ordered system with spin orbit magnetism, where the order parameter has a net spin current and no net magnetization in both two dimension and three dimension. Starting from a Fermi liquid theory, similar to that for a weak ferromagnet, I have shown that this excitation emerges from an exotic magnetic Fermi liquid state that is protected by a generalized Pomeranchuck condition. I derive the propagating mode using the Landau kinetic equation, and find that the dispersion of the mode has a $sqrt q$ behavior in leading order in 2D. I also find an instability toward superconductivity induced by this exotic mode, and a further analysis based on the forward scattering sum rule strongly suggests that this superconductivity has triplet pairing symmetry. I perform similar studies in the 3D case, with a slightly different magnetic system and find that the mode leads to a Lifshitz-like instability most likely toward an inhomogeneous magnetic state in one of the phases. I also study the collective modes in itinerant ferromagnetic system, which is related to the $F_0^a$ pomeranchuck instability. Using FFLT, I obtained the well-known magnon (Nambu-Goldstone) mode and a gapped mode that was first found by Bedell and Blagoev. I have identified this mode as the Higgs boson (amplitude mode) of a ferromagnetic metal. This is identified as the Higgs since it can be shown that it corresponds to a fluctuation of the amplitude of the order parameter. I use this model to describe the itinerant-electron ferromagnetic material MnSi. By fitting the model with the existing experimental results, I calculate the dynamical structure function and see well-defined peaks contributed from the magnon and the Higgs. From my estimates of the relative intensity of the Higgs amplitude mode I expect that it can be seen in neutron scattering experiments on MnSi. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

The principal aim of this Thesis is the synthesis and characterisation of a range of novel liquid crystals designed to exhibit the twist-bend nematic phase (NTB), in order to enhance our understanding of the relationships between molecular structure and the observation of NTB behaviour. Moreover, the inclusion of chiral fragments allowed the effects of molecular chirality on the structure of the NTB phase, specifically the chiral twist-bend nematic phase, N*TB, to be studied. In Chapter 3, a series of non-symmetric odd-membered liquid crystal dimers are prepared and the terminal chain length m is varied. A change in the local molecular structure from intercalated to bilayer is seen on increasing m, but this has no apparent effect on the stability of both the nematic and twist-bend nematic phases, which show a regular dependence on m. A novel twist-bend smectic phase is reported. Chapter 4 investigates the effects of branching this terminal chain on phase behaviour. It is evident that in dimers with a shorter spacer, branching destabilises the N and NTB phases while stabilising smectic behaviour, but in longer homologues smectic behaviour is also destabilised. Chapter 5 explores the effect of molecular bulk on phase behaviour, specifically the stability of the NTB phase, by the incorporation of a pyrene moiety. This group supresses crystallisation such that stable, low temperature NTB phases are formed despite the bulky group. Chapters 6 and 7 study the inclusion of chiral moieties in bent-shaped, odd-membered dimers: specifically, 2-methylbutyl, 1-methylheptyl (6) and lactic esters (7). New examples of the rarely observed chiral twist-bend nematic phase are seen. Phase behaviour is investigated and compared to achiral and racemic analogues. Chapter 8 describes the mesogenic behaviour of molecular complexes assembled by hydrogen bonding between both achiral and chiral stilbazole-based and benzoic acid-based fragments. A selection of the complexes exhibit the N(*)TB phase despite only one or neither component being mesogenic.

Thesis (Ph.D.)--Boston University

Foram estudadas as seguintes mesofases liotrópicas tipo I, que se orientam espontaneamente em presença de campo magnético, com o eixo de simetria paralelo ao campo: laurato de potássio/KCl/H2O e decilsulfato de césio/CsNO3/H2O; foi estudada também a mesofase liotrópica laurato de potássio/H2O, que não apresenta a propriedade de orientação magnética espontânea. Foram utilizadas as técnicas da difração de raios-X em alto e baixo ângulos e, de forma acessória, microscopia óptica de luz polarizada, calorimetria diferencial de varredura e criofratura( freeze etching). A mesofases foram acondicionadas em diferentes tipos de porta-amostras com e sem tratamento químico de superfície, submetidas a campos magnético e elétrico, bem como a variações de temperatura. Esse estudo possibilitou a identificação de geometria das unidades difratoras, confirmando o modelo de micelas cilíndricas, para o tipo I, bem como forneceu evidências da influência dos efeitos de superfície e da formação de agregados de micelas com dimensões variadas, que originaram os padrões de difração. Foi confirmada a coexistência das fases hexagonal infinita e tipo I em equilíbrio termodinâmico. Foi construído um modelo de agregados de micelas ajustado aos resultados experimentais do espalhamento de raios-X. A formação desses agregados pode ser explicada pelo balanço das interações atrativa de van der Waals, repulsiva coulombiana e de volume excluído, esta última a partir de considerações sobre a solvatação das micelas de anfifílico no meio aquoso. / We studied the following type I lyotropic mesophases, which are oriented spontaneously in the presence of magnetic field, with the symmetry axis parallel to the field: potassium laurate/KCl/H2O and cesium decilsulfate/CsNO3/H2O; was also studied lyotropic mesophase potassium laurate /H2O, which does not exhibit the property of spontaneous magnetic orientation. We used the techniques of X-ray diffraction at high and low angles, and an ancillary, polarized light microscopy, differential scanning calorimetry and cryofracture (\"freeze etching\").

No description available.

Foram estudadas as seguintes mesofases liotrópicas tipo I, que se orientam espontaneamente em presença de campo magnético, com o eixo de simetria paralelo ao campo: laurato de potássio/KCl/H2O e decilsulfato de césio/CsNO3/H2O; foi estudada também a mesofase liotrópica laurato de potássio/H2O, que não apresenta a propriedade de orientação magnética espontânea. Foram utilizadas as técnicas da difração de raios-X em alto e baixo ângulos e, de forma acessória, microscopia óptica de luz polarizada, calorimetria diferencial de varredura e criofratura( freeze etching). A mesofases foram acondicionadas em diferentes tipos de porta-amostras com e sem tratamento químico de superfície, submetidas a campos magnético e elétrico, bem como a variações de temperatura. Esse estudo possibilitou a identificação de geometria das unidades difratoras, confirmando o modelo de micelas cilíndricas, para o tipo I, bem como forneceu evidências da influência dos efeitos de superfície e da formação de agregados de micelas com dimensões variadas, que originaram os padrões de difração. Foi confirmada a coexistência das fases hexagonal infinita e tipo I em equilíbrio termodinâmico. Foi construído um modelo de agregados de micelas ajustado aos resultados experimentais do espalhamento de raios-X. A formação desses agregados pode ser explicada pelo balanço das interações atrativa de van der Waals, repulsiva coulombiana e de volume excluído, esta última a partir de considerações sobre a solvatação das micelas de anfifílico no meio aquoso. / We studied the following type I lyotropic mesophases, which are oriented spontaneously in the presence of magnetic field, with the symmetry axis parallel to the field: potassium laurate/KCl/H2O and cesium decilsulfate/CsNO3/H2O; was also studied lyotropic mesophase potassium laurate /H2O, which does not exhibit the property of spontaneous magnetic orientation. We used the techniques of X-ray diffraction at high and low angles, and an ancillary, polarized light microscopy, differential scanning calorimetry and cryofracture (\"freeze etching\").

For the last 20 years, there has been considerable interest in chiral nematic liquid crystal band edge lasers. The birefringent molecules of chiral nematic liquid crystals form a periodic helical structure, which results in a photonic bandgap for circularly polarised light with the same sense of rotation as the helix. A large increase in effective gain is seen for a fluorescent gain medium within the liquid crystal at the band edges, resulting in lasing. Applications of liquid crystal lasers could include miniature medical diagnostic tools, large-area holographic laser displays, and environmental sensing. The wavelength of emission from dye-doped chiral nematic liquid crystals is highly flexible, with lasers demonstrated across the visible range and near infra-red. This thesis investigates two routes for improving the functionality of chiral nematic liquid crystal lasers, supported by mathematical modelling of expected lasing wavelengths based on reflection and transmission by anisotropic layers. Perovskite is tested as a replacement for fluorescent laser dyes as a gain medium,both in the form of quantum dots dispersed in liquid crystal, and as films placed in liquid crystal structures. It is shown that while the perovskite tested provides some emission, it is not compatible for lasing in these devices, and suggestions for building on these results are made. In-plane switching is tested and developed as a means to achieve tuning of the laser wavelength, demonstrating a continuous wavelength shift of 15 nm, from 600.71 nm to 585.03 nm, over a voltage range of 100 V. This is an improvement on previous tuning in related devices, and may be extended with optimisation of cell thickness,electrode geometry, and initial lasing wavelength. Accurate descriptions of the refractive index profile of the liquid crystal and perovskite are developed and included in mathematical modelling, in addition to descriptions of the wavelength-dependent gain of a laser dye and perovskite. Suggestions for developing this modelling are made, particularly by the inclusion of accurate modelling of the distortion caused by in-plane switching.

Tao, Yin = 納米線在液晶中的動力學 / 陶寅. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Abstracts in English and Chinese. / Tao, Yin = Na mi xian zai ye jing zhong de dong li xue / Tao Yin. / Abstract --- p.I / 摘要 --- p.III / Acknowledgement --- p.IV / List of Figures --- p.VIII / List of Tables --- p.XV / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1. --- Background --- p.1 / Chapter 1.2. --- Review of Liquid Crystals --- p.2 / Chapter 1.2.1. --- Basic concepts --- p.2 / Chapter 1.2.2. --- Physical Properties of liquid crystals --- p.5 / Chapter 1.3. --- Manipulation of nanowires in suspensions --- p.8 / Chapter 1.3.1. --- Longitudinal Anchoring of liquid crystals --- p.8 / Chapter 1.3.2. --- Dielectrophoretic force and torque --- p.12 / Chapter 1.3.3. --- Measurement of conductivity --- p.15 / Chapter 1.4. --- Our motivation and work --- p.17 / Reference --- p.19 / Chapter Chapter 2 --- Experiments --- p.22 / Chapter 2.1. --- Nematic Liquid Crystal Cell Design and Fabrication --- p.22 / Chapter 2.1.1. --- Parallel Plate Capacitor like Liquid Crystal Cell --- p.22 / Chapter 2.1.2. --- In-Plane Switching Liquid Crystal Cell --- p.23 / Chapter 2.2. --- Filling of liquid crystals and dispersing nanowires --- p.28 / Chapter 2.3. --- Measurements --- p.30 / Chapter 2.3.1. --- Measurement of alignment and reorientation of the nanowires --- p.30 / Chapter 2.3.2. --- Measurements of the optical transmittance of liquid crystal cell --- p.31 / Chapter 2.4. --- Experimental Procedures --- p.33 / Chapter 2.4.1. --- Study of the relaxation of liquid crystals and nanowires --- p.33 / Chapter 2.4.2. --- Study of response of liquid crystals and nanowires to applied E field --- p.34 / Reference --- p.35 / Chapter Chapter 3 --- Numerical simulations of the motion of liquid crystals --- p.36 / Chapter 3.1. --- Leslie-Ericsson equation --- p.36 / Chapter 3.2. --- Response and relaxation of liquid crystals --- p.39 / Chapter 3.2.1. --- Parallel plate capacitor like liquid crystal cells --- p.39 / Chapter 3.2.2. --- In-plane switching liquid crystal cells --- p.45 / Reference --- p.49 / Chapter Chapter 4 --- Method of analysis --- p.50 / Chapter 4.1. --- Deduction of the orientation of nanowires --- p.50 / Chapter 4.1.1. --- Parallel plate capacitor like liquid crystal cell --- p.50 / Chapter 4.1.2. --- In-plane switching liquid crystal cells --- p.52 / Chapter 4.2. --- Methods of curve fitting to experimental data --- p.54 / Chapter 4.2.1. --- Procedures of fitting the curves of transmission --- p.54 / Chapter 4.2.2. --- Procedures of fitting the curves of angle β (t) and φ (t)…… --- p.57 / Reference --- p.64 / Chapter Chapter 5 --- Results and discussion --- p.65 / Chapter 5.1. --- Study of the relaxation of nanowires and liquid crystals --- p.65 / Chapter 5.1.1. --- Dependence on the length of nanowires --- p.65 / Chapter 5.1.2. --- Dependence on the temperature of liquid crystals --- p.82 / Chapter 5.2. --- Study of the responses of nanowires and liquid crystals to E field --- p.89 / Chapter 5.2.1. --- Dependence on the applied E field --- p.89 / Chapter 5.2.2. --- Dependence on the length of nanowires --- p.112 / Chapter 5.2.3. --- Dependence on the temperature of liquid crystal --- p.116 / Reference --- p.122 / Chapter Chapter 6 --- Conclusions --- p.123 / Appendix 1 --- p.125 / Appendix 2 --- p.132

Tam, Yiu Ho = 納米線在液晶中的取向研究 / 譚耀豪. / "November 2009." / Accompanying CD-ROM contains data files. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 79-83). / Abstracts in English and Chinese. / Library's copy: lacks accompanying CD-ROM. / Tam, Yiu Ho = Na mi xian zai ye jing zhong de qu xiang yan jiu / Tan Yaohao. / Abstract --- p.1 / 摘要 --- p.2 / Acknowledgements --- p.3 / Table of contents --- p.4 / Chapter Chapter 1 --- Introduction --- p.8 / Chapter 1.1 --- Background --- p.8 / Chapter 1.2 --- Review of Liquid crystals --- p.8 / Chapter 1.2.1 --- Molecular structure --- p.8 / Chapter 1.2.2 --- Phases --- p.10 / Chapter 1.2.3 --- Classification of liquid crystalline phases --- p.11 / Chapter 1.2.4 --- Elastic property --- p.12 / Chapter 1.2.5 --- Electrical property --- p.13 / Chapter 1.2.6 --- Optical property --- p.14 / Chapter 1.2.7 --- Alignment methods of liquid crystals --- p.14 / Chapter 1.2.8 --- Dynamics of the director of liquid crystals --- p.15 / Chapter 1.2.9 --- Transmittance calculations --- p.17 / Chapter 1.3 --- Interactions between liquid crystal and nanorods --- p.19 / Chapter 1.3.1 --- Longitudinal anchoring --- p.19 / Chapter 1.3.2 --- Theoretical model of the elastic interaction --- p.20 / Chapter 1.4 --- Motivations --- p.22 / Chapter 1.5 --- Our work --- p.23 / Chapter 1.6 --- Overview of the thesis --- p.23 / Chapter Chapter 2 --- Experiments --- p.24 / Chapter 2.1 --- Cell fabrications --- p.24 / Chapter 2.2 --- Filling of liquid crystal and dispersing nanorods --- p.26 / Chapter 2.3 --- Measurements --- p.27 / Chapter 2.3.1 --- Measurements of alignment and deduction of the orientation of nanorods --- p.27 / Chapter 2.3.2 --- Measurements of the optical transmittance of liquid crystal cells --- p.27 / Chapter 2.4 --- Experimental procedures --- p.29 / Chapter 2.4.1 --- Study of the statics of nanorods and liquid crystal --- p.29 / Chapter 2.4.2 --- Study of the dynamics of nanorods and liquid crystal --- p.30 / Chapter Chapter 3 --- Numerical solutions of the equations of motions --- p.31 / Chapter 3.1 --- Solving procedures --- p.31 / Chapter 3.1.1 --- Conversion of differential equations into difference equations --- p.31 / Chapter 3.1.2 --- Solving algorithm --- p.33 / Chapter 3.2 --- Comparison of numerical and analytical solutions --- p.35 / Chapter 3.2.1 --- Analytic solution of a simplified equation of motion --- p.35 / Chapter 3.2.2 --- Checking for the agreement between the numerical and analytic results --- p.36 / Chapter 3.2.3 --- Checking for the accuracy of the numerical results --- p.39 / Chapter Chapter 4 --- Method of analysis --- p.41 / Chapter 4.1 --- Deduction of the orientation of nanorods --- p.41 / Chapter 4.2 --- Method of curves fitting to experimental data --- p.43 / Chapter 4.2.1 --- Procedures of fitting the transmission curves --- p.43 / Chapter 4.2.2 --- Procedures of fitting the curves of angle ß --- p.44 / Chapter Chapter 5 --- Results and discussion --- p.48 / Chapter 5.1 --- Study of the statics of nanorods and liquid crystal --- p.48 / Chapter 5.1.1 --- Study of the alignment ability of liquid crystal on the nanorods --- p.48 / Chapter 5.1.2 --- Study of the longitudinal anchoring effect of liquid crystal on the nanorods --- p.54 / Chapter 5.2 --- Study of the dynamics of nanorods and the liquid crystal --- p.57 / Chapter 5.2.1 --- Dependence on the length of nanorods --- p.57 / Chapter 5.2.1 --- Temperature dependence on the LC-nanorod interaction --- p.66 / Chapter Chapter 6 --- Conclusions --- p.76 / References --- p.79 / Appendices --- p.84

Separations depend on the molecular interactions occurring on retentive surfaces. Much time and effort is paid in the design and manufacture of chromatographic surfaces that enhance separation capability. This thesis explores some of the design concepts currently available in the market place, and while doing so, investigates the mode of retention on a range of solute species. The information gained from the investigation of the retention and thermodynamic retention behaviour of stationary phases, along with molecular modelling carried out on their stationary phase ligand conformation assists in the design of stationary phase materials that enhance separations. Results from this study indicate that the aromatic functionality on the Synergi-polar-RP column may be diminished, due to the orientation of the phenyl ring on the stationary phase surface. / Doctor of Philosophy (PhD)