Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2007. / Davidovic, Dragomir, Committee Member ; Kennedy, T.A. Brian, Committee Member ; Chapman, Mike, Committee Member ; Raman, Chandra, Committee Chair ; Bunz, Uwe, Committee Member.

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by Lin Lap-Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves [105]-109). / Text in English; abstracts in English and Chinese. / by Lin Lap-Ming. / Abstract --- p.i / Acknowledgement --- p.ii / Contents --- p.iii / List of Figures --- p.vi / List of Tables --- p.ix / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Physical Motivation --- p.1 / Chapter 1.2 --- Quasi-Normal Modes --- p.3 / Chapter 1.3 --- Superfluidity in Neutron Stars --- p.7 / Chapter 1.4 --- Outline of this Thesis --- p.9 / Chapter Chapter 2. --- The Ordinary Perfect Fluid Neutron Stars --- p.11 / Chapter 2.1 --- The Equilibrium Neutron Star Models --- p.11 / Chapter 2.2 --- Non-Radial Oscillations of Neutron Stars --- p.14 / Chapter 2.3 --- The Quasi-Normal Modes of Stars --- p.17 / Chapter 2.3.1 --- The Fluid Modes --- p.17 / Chapter 2.3.2 --- The Spacetime Modes --- p.18 / Chapter Chapter 3. --- The General Relativistic Superfluid Formalism --- p.22 / Chapter 3.1 --- The Carter Formalism --- p.22 / Chapter 3.2 --- The Master Function --- p.25 / Chapter Chapter 4. --- The Equilibrium Superfluid Neutron Stars --- p.27 / Chapter 4.1 --- The Equilibrium Configurations --- p.27 / Chapter 4.2 --- Initial and Boundary Conditions --- p.34 / Chapter 4.3 --- Polytropic Models --- p.36 / Chapter Chapter 5. --- Non-Radial Oscillations of Superfluid Neutron Stars --- p.40 / Chapter 5.1 --- The Linearized Field Equations Inside the Star --- p.40 / Chapter 5.1.1 --- Equations for Even-Parity Perturbations --- p.45 / Chapter 5.1.2 --- Equations for Odd-Parity Perturbations --- p.48 / Chapter 5.2 --- Initial and Boundary Conditions --- p.49 / Chapter 5.2.1 --- Radial Integration Initial Conditions --- p.49 / Chapter 5.2.2 --- Boundary conditions at the Surface --- p.55 / Chapter 5.3 --- The Linearized Field Equations Outside the Star --- p.57 / Chapter 5.4 --- Numerical Technique --- p.60 / Chapter Chapter 6. --- Quasi-Normal Modes Extraction --- p.62 / Chapter 6.1 --- Numerical Techniques for Quasi-Normal Modes Extraction --- p.62 / Chapter 6.2 --- The Leaver Series --- p.64 / Chapter 6.3 --- The Graphical Method --- p.67 / Chapter Chapter 7. --- The Quasi-Normal Modes of Superfluid Neutron Stars --- p.69 / Chapter 7.1 --- Polytropic Models --- p.69 / Chapter 7.1.1 --- The w-modes --- p.70 / Chapter 7.1.2 --- The f- and p-modes --- p.74 / Chapter 7.2 --- Ideal Neutron-Proton-Electron Gas --- p.82 / Chapter 7.3 --- Convergence Tests and Accuracy --- p.92 / Chapter Chapter 8. --- Conclusion --- p.95 / Appendix A. Speeds of Sound --- p.97 / Appendix B. Equations for Radial Oscillations --- p.99 / Appendix C. Numerical Technique for Solving Leaver's Series --- p.101 / Appendix D. Scaling in Numerical Calculations --- p.103 / Bibliography --- p.105

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Wong, Ka Sin Jamie = 超流性對中子星振盪的影響 / 黃家倩. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (p. 212-215). / Abstract also in Chinese. / Wong, Ka Sin Jamie = Chao liu xing dui zhong zi xing zhen dang de ying xiang / Huang Jiaqian. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivations --- p.1 / Chapter 1.2 --- Outline of Thesis --- p.3 / Chapter 1.3 --- Notation and Conventions --- p.4 / Chapter 2 --- The Relativistic Superfluid Star --- p.7 / Chapter 2.1 --- The Carter Formalism --- p.7 / Chapter 2.2 --- The Equilibrium Superfluid Star Models --- p.9 / Chapter 2.3 --- Non-Radial Oscillations of Superfluid Neutron Star --- p.13 / Chapter 2.3.1 --- Equations for Even-Parity Perturbations --- p.16 / Chapter 2.3.2 --- Equations for Odd-Parity Perturbations --- p.18 / Chapter 2.3.3 --- Linearised Equations Outside the Star --- p.19 / Chapter 2.3.4 --- Boundary Conditions for Quasinormal Modes --- p.21 / Chapter 2.3.5 --- Quasinormal Mode Spectrum of Superfluid Stars --- p.22 / Chapter 3 --- Universality in Superfluidf-mode --- p.25 / Chapter 3.1 --- What is an f-mode? --- p.25 / Chapter 3.2 --- Uncoupled Polytropic Master Function for Superfluid Stars --- p.27 / Chapter 3.3 --- Reparametrising the Uncoupled Polytropic Master Function --- p.29 / Chapter 3.4 --- f-mode Frequency of Uncoupled Polytropic Superfluid Stars --- p.30 / Chapter 3.5 --- "Derivation of Superfluid Mode Frequency for a Newtonian Sphere of Two Homogeneous, Incompressible, Uncoupled Fluids" --- p.40 / Chapter 4 --- Effects of Entrainment on Superfluid Mode Frequencies --- p.45 / Chapter 4.1 --- What is entrainment? --- p.45 / Chapter 4.2 --- Numerical Results --- p.48 / Chapter 4.3 --- Newtonian Variational Formalism --- p.51 / Chapter 4.4 --- Deriving the Approximate First Order Shift --- p.54 / Chapter 5 --- Variational Principle for Polar Modes --- p.60 / Chapter 5.1 --- Alternative Set of Perturbed Equations for Superfluid Neutron Star --- p.60 / Chapter 5.2 --- Boundary Conditions for Polar Quasinormal Modes --- p.64 / Chapter 5.3 --- Deriving the Variational Principle --- p.65 / Chapter 5.4 --- Recasting the Principle in Abstract Notation --- p.67 / Chapter 5.5 --- Doing Away with the Constraint Equations --- p.70 / Chapter 5.6 --- Regarding the Purely Real Nature of the First Order Term --- p.71 / Chapter 5.7 --- First Order Shift in Mode Frequency due to Entrainment --- p.74 / Chapter 6 --- Excitation of Quasinormal Modes --- p.77 / Chapter 6.1 --- Perturbed Equations Inside the Star --- p.77 / Chapter 6.2 --- Perturbed Equations Outside the Star --- p.78 / Chapter 6.3 --- Circular Orbits in Schwarzschild Spacetime --- p.80 / Chapter 6.4 --- Calculation of Source Term --- p.82 / Chapter 6.5 --- Determination of Amplitude --- p.85 / Chapter 6.6 --- Numerical Procedures --- p.86 / Chapter 6.7 --- Numerical Results --- p.89 / Chapter 7 --- Stability of Non-rotating Newtonian Superfluid Stars to Non-radial Oscillations --- p.91 / Chapter 7.1 --- Introduction --- p.91 / Chapter 7.2 --- Two-fluid Systems --- p.93 / Chapter 7.3 --- A Review of Basic Thermodynamics --- p.96 / Chapter 7.4 --- Perturbed System of Equations --- p.100 / Chapter 7.5 --- Schwarzschild Discriminant --- p.102 / Chapter 7.6 --- Variational Principle for Mode Frequency --- p.105 / Chapter 7.7 --- Stability of Polar Oscillations --- p.108 / Chapter 7.7.1 --- A Sufficient Condition for Stability --- p.109 / Chapter 7.7.2 --- A Necessary and Sufficient Condition for the Occurrence of Zero-frequency Modes --- p.112 / Chapter 7.7.3 --- Conditions for Instability --- p.119 / Chapter 7.8 --- A Little Application to Zero-temperature Superfluid Star --- p.121 / Chapter 7.9 --- Inclusion of Non-dissipative Magnus-typed Force --- p.122 / Chapter 7.10 --- Conclusion --- p.123 / Chapter 8 --- A Single Scalar Governing Stability of Newtonian Superfluid Neutron Stars to Non-radial Oscillations --- p.125 / Chapter 8.1 --- Introduction --- p.125 / Chapter 8.2 --- Summary of Results of the Last Chapter --- p.126 / Chapter 8.3 --- Motivation --- p.129 / Chapter 8.4 --- Occurrence of Neutral Modes --- p.131 / Chapter 8.5 --- S> 0 Implies Stability to Non-radial Oscillations --- p.133 / Chapter 8.6 --- S < 0 On a Finite Interval of r Implies Instability --- p.135 / Chapter 8.7 --- Conclusion --- p.137 / Chapter 9 --- Lagrangian Perturbation Theory for Rotating Non-relativistic Superfluid Stars --- p.138 / Chapter 9.1 --- Perturbation Operators --- p.139 / Chapter 9.2 --- Perturbing the Dynamical Equations --- p.143 / Chapter 9.3 --- Variational Principle and Symplectic Structure --- p.147 / Chapter 9.4 --- Showing Antisymmetry of B --- p.149 / Chapter 9.5 --- Showing Symmetry of C --- p.154 / Chapter 9.6 --- Canonical Displacement --- p.157 / Chapter 9.7 --- Using Canonical Energy in Stability Calculation --- p.163 / Chapter 9.8 --- Instability of r-mode for a Superfluid Star --- p.164 / Chapter 9.9 --- CFS Instability of Normal Modes --- p.169 / Chapter 10 --- Conclusion --- p.172 / Chapter A --- Some Useful Relations --- p.174 / Chapter B --- Derivation of Equations Given in Section 5.1 --- p.176 / Chapter C --- Order Analysis of Quantities at Stellar Radius --- p.179 / Chapter D --- Condition for the Occurrence of Non-radiating Modes --- p.182 / Chapter E --- Perturbed Equations for Polar Oscillations and Boundary Conditions --- p.186 / Chapter F --- Deriving the Variational Principle --- p.191 / Chapter G --- Discerning Similarity with Ordinary-fluid Variational Expression --- p.195 / Chapter G.l --- T'=0 --- p.195 / Chapter G.2 --- T'=0 --- p.199 / Chapter H --- A Condition for Instability of a Dynamical System --- p.202 / Chapter I --- Derivation of Zeroth-order r-mode Frequency --- p.205 / Chapter J --- Spin-s Spherical Harmonics --- p.207 / Chapter J.1 --- Spin-s Quantities --- p.207 / Chapter J.2 --- Motivation of Spin-s Spherical Harmonics --- p.208 / Chapter J.3 --- Proof of a Relation --- p.210 / Bibliography --- p.212

Conventional electronics rely on the transport of electrons through a circuit to carry information. This comes with ever-present Joule heating as a result of the resistive scattering of electrons. Recent works in the field of spintronics have focused on using magnetic excitations (e.g., spin waves) instead of electrons as a means of information transport without Joule heating. However, realizing long distance information transport using conventional spin waves has proven difficult owing to their diffusive nature and the exponential decay of spin current. Theoretical studies have proposed a new form of magnetization dynamics, referred to as superfluid-like spin transport, as a way to overcome this shortfall. Instead of decaying exponentially with distance, the spin current associated with superfluid-like spin transport decays linearly with distance, potentially allowing for information transport beyond the micron-scale. In this dissertation, I discuss the work that I have done towards realizing this novel phenomenon in a metallic, ferromagnetic system. Results on a reduced damping and reduced magnetic moment Fe-based alloy, micromagnetic simulations that use established domain wall physics to explain superfluid-like spin transport, and an investigation of spin torques found in a current-in-plane spin valve structure with broken in-plane symmetry for excitation of superfluid-like spin transport dynamics are discussed. I conclude by discussing what steps remain before superfluid-like spin transport can be measured in an experimental system as well as the impacts this work could have on the wider spintronics field. This work was supported in part by National Science Foundation, Grant No. DMR-2003914. / Doctor of Philosophy / All of the electronics devices we use every day depend on tiny, charged particles called electrons moving through a wire. These particles bounce off of and collide with defects within that wire and cause the wire to heat up, dissipating their energy to the surrounding environment. If this could be avoided, the overall power needed to operate our devices could be lowered. To alleviate this problem, scientists take advantage of another property of the electron, its spin (which gives rise to magnetism), to send signals. Since the electron spin can interact with the spin of nearby electrons, information can be transported this way without actually moving the electrons themselves. These magnetic signals can be thought of as the electron spin wiggling a small amount about its axis, somewhat akin to a precessing top. The downside to these magnetic signals is that they decay away very quickly, typically much quicker than electron currents. In this dissertation, I focus on using a different form of magnetic signals, one that can be thought of like a fluid flowing through a pipe, to send information much further than before without significant energy losses. This phenomenon, which I call ``superfluid-like spin transport,'' has the potential to dramatically alter the future development path of next-generation devices. In the first experiment, I discuss the work done to choose a suitable material platform that can host superfluid-like spin transport. Starting with the common magnet iron, we show that by mixing it with the correct non-magnetic material, it is possible to improve the magnetic properties in a way that is beneficial to superfluid-like spin transport. In the next experiment, computer simulations were used to understand how superfluid-like spin transport might behave in a future device. We find that the fluid-like behavior found in this phenomenon can actually be understood by imagining a train of rigid particle-like entities being packed closely together. In the final experiment, I investigate whether a new and potentially simpler device geometry can be used to start the flow of superfluid-like spin transport. It turns out that the mechanism needed to start the flow is surprisingly weak in the material system studied. While this work does not achieve superfluid-like spin transport, it has taken essential steps towards understanding how one might do so in the future using common materials in an easy-to-make manner. I conclude by offering my thoughts of what the next steps would be as well as impacts this work might have on future next-generation energy-efficient devices.

Liu, Xiaopi = 光格子势中玻色爱因斯坦凝聚体的压缩,纠缠与激发谱 / 刘小披. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 97-100). / Abstracts in English and Chinese. / Liu, Xiaopi = Guang ge zi shi zhong bo se ai yin si tan ning ju ti de ya suo, jiu chan yu ji fa pu / Liu Xiaopi. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Review of Superfluidity and B.E. Condensation --- p.1 / Chapter 1.2 --- Our Understanding of superfluidity --- p.4 / Chapter 1.3 --- Non-classicality in Quantum Mechanics --- p.8 / Chapter 2 --- One-Component BECs in optical lattices --- p.16 / Chapter 2.1 --- Introduction: The Hamiltonian --- p.16 / Chapter 2.2 --- The Hamiltonian in Quasi-momentum space --- p.19 / Chapter 2.3 --- Bogoliubov Method and Equation of Motion --- p.21 / Chapter 2.3.1 --- Squeezing and Condensation --- p.27 / Chapter 2.3.2 --- Two-mode Entanglement and Squeezing --- p.31 / Chapter 3 --- Matrix method approach to ground state BECs --- p.39 / Chapter 3.1 --- Matrix method --- p.39 / Chapter 3.2 --- Ground state and Particle Distribution --- p.42 / Chapter 3.3 --- Correlation in Pair Ground State --- p.46 / Chapter 4 --- Attractive BECs in optical lattices --- p.50 / Chapter 5 --- 2-component BECs in optical lattice --- p.56 / Chapter 5.1 --- Model Hamiltonian --- p.56 / Chapter 5.2 --- Excitation Spectrum and Critical super-fluid velocity --- p.59 / Chapter 5.3 --- Excitation spectrum and Phase Separation Dynamics --- p.63 / Chapter 5.4 --- Excitation Spectrum for Asymmetric 2-component BECs --- p.67 / Chapter 6 --- Multi-Mode Squeezing of 2-component BECs in optical lattices --- p.69 / Chapter 6.1 --- Simultaneous Diagonalization --- p.69 / Chapter 6.2 --- Equation of Motion and Variance Matrix --- p.70 / Chapter 6.3 --- U(n) Squeezing of Variance Matrix --- p.75 / Chapter 6.4 --- Squeezing in the case qA≠ qB and nA≠ nB --- p.82 / Chapter 7 --- Entanglement between 2-component BECs in optical lattices --- p.83 / Chapter 7.1 --- Variance matrix in block diagonal --- p.83 / Chapter 7.2 --- 2-component entangled variance matrix --- p.86 / Chapter 7.3 --- Logarithmic negativity --- p.89 / Chapter 7.4 --- Beat oscillation mode of logarithmic negativity --- p.91 / Chapter 8 --- Conclusion and Outlook --- p.95 / Bibliography --- p.97