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Articles 1 - 30 of 52
Full-Text Articles in Condensed Matter Physics
Quantum Chaos, Integrability, And Hydrodynamics In Nonequilibrium Quantum Matter, Javier Lopez Piqueres
Quantum Chaos, Integrability, And Hydrodynamics In Nonequilibrium Quantum Matter, Javier Lopez Piqueres
Doctoral Dissertations
It is well-known that the Hilbert space of a quantum many-body system grows exponentially with the number of particles in the system. Drive the system out of equilibrium so that the degrees of freedom are now dynamic and the result is an extremely complicated problem. With that comes a vast landscape of new physics, which we are just recently starting to explore. In this proposal, we study the dynam- ics of two paradigmatic classes of quantum many-body systems: quantum chaotic and integrable systems. We leverage certain tools commonly employed in equilibrium many-body physics, as well as others tailored to the …
Experiments With Monopoles, Rings And Knots In Spinor Bose-Einstein Condensates, Alina A. Blinova
Experiments With Monopoles, Rings And Knots In Spinor Bose-Einstein Condensates, Alina A. Blinova
Doctoral Dissertations
Topological excitations are ubiquitous in nature, their charge being a naturally-quantized, conserved quantity that can exhibit particle-like behavior. Spinor Bose-Einstein condensates (BECs) are an exceptionally versatile system for the study and exploration of topological excitations. Between the spin-1 and spin-2 87Rb condensates there are seven possible broken-symmetry magnetic phases, with each one hosting unique opportunities for topological defects. We have created and observed several novel topological excitations in a spinor 87Rb BEC. In this dissertation I present and discuss three principal experimental findings: (1) The discovery of an Alice ring, or a half-quantum vortex ring, emerging from a …
Self-Limiting Morphologies In Geometrically Frustrated Assemblies, Douglas M. Hall
Self-Limiting Morphologies In Geometrically Frustrated Assemblies, Douglas M. Hall
Doctoral Dissertations
Geometrically frustrated assembly, where locally preferred motifs are incompatible with constraints on global ordering of the assembly, may result in a super-extensive energy penalty to assembly growth and self-limitation of the assembly size. Using theory and simulation, we study how this mechanism may also shape the assembly's boundary and its interior packing, which are distinct morphological changes. In Chapter 1, we provide some background and a theoretical framework for understanding self-limiting behavior due to geometric frustration. Three distinct projects are detailed in the subsequent chapters: original numerical results are presented on competing responses to frustration in helical bundles made of …
Synthesis And Assembly Of Polymer Materials At Interfaces, Xiaoshuang Wei
Synthesis And Assembly Of Polymer Materials At Interfaces, Xiaoshuang Wei
Doctoral Dissertations
The overarching goal of the thesis is to understand growth and assembly of polymer materials at interfaces. Chapter 2 and Chapter 3 study simultaneous polymer growth and assembly at fluid interfaces, where in-situ photopolymerization and vapor phase deposition were utilized to grow polymers, respectively. Chapter 4 leverages capillary condensation to pattern polymer growth at solid substrates. Chapter 1 provides background information on polymer materials at interfaces, and vapor phase deposition method (initiated chemical vapor deposition, iCVD) to grow polymers. This chapter also reviews polymer thin film wetting, and colloidal assemblies at interfaces. In Chapter 2, we demonstrate the preparation …
Symmetry Breaking Effects In Low-Dimensional Quantum Systems, Ke Wang
Symmetry Breaking Effects In Low-Dimensional Quantum Systems, Ke Wang
Doctoral Dissertations
Quantum criticality in low-dimensional quantum systems is known to host exotic behaviors. In quantum one-dimension (1D), the emerging conformal group contains infinite generators, and conformal techniques, e.g., operator product expansion, give accurate and universal descriptions of underlying systems. In quantum two-dimension (2D), the electronic interaction causes singular corrections to Fermi-liquids characteristics. Meanwhile, the Dirac fermions in topological 2D materials can greatly enrich emerging phenomena. In this thesis, we study the symmetry-breaking effects of low-dimensional quantum criticality. In 1D, we consider two cases: time-reversal symmetry (TRS) breaking in the Majorana conformal field theory (CFT) and the absence of conformal symmetry in …
Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian
Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian
Doctoral Dissertations
The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …
Reservoir Engineering Of Multi-Photon States In Circuit Quantum Electrodynamics, Jeffrey M. Gertler
Reservoir Engineering Of Multi-Photon States In Circuit Quantum Electrodynamics, Jeffrey M. Gertler
Doctoral Dissertations
The field of experimental quantum information has made significant progress towards useful computation but has been handicapped by the dissipative nature of physical qubits. Except for unwieldy and unrealized topological qubits, all quantum information systems experience natural dissipation, which limits the time scale for useful computation. However, this same dissipation, which induces errors requiring quantum error correction (QEC), can be used as a resource to perform a variety of important and unrealized tasks. In this thesis I discuss research into three uses of dissipation: manifold stabilization, state transfer, and QEC. With reservoir engineering, these tasks can be addressed in an …
Anomalous Transport, Quasiperiodicity, And Measurement Induced Phase Transitions, Utkarsh Agrawal
Anomalous Transport, Quasiperiodicity, And Measurement Induced Phase Transitions, Utkarsh Agrawal
Doctoral Dissertations
With the advent of the noisy-intermediate scale quantum (NISQ) era quantum computers are increasingly becoming a reality of the near future. Though universal computation still seems daunting, a great part of the excitement is about using quantum simulators to solve fundamental problems in fields ranging from quantum gravity to quantum many-body systems. This so-called second quantum revolution rests on two pillars. First, the ability to have precise control over experimental degrees of freedom is crucial for the realization of NISQ devices. Significant progress in the control and manipulation of qubits, atoms, and ions, as well as their interactions, has not …
Collective Motion And Phase Diagram Of Self-Propelled Vibrated Hard Squares, Zhejun Shen
Collective Motion And Phase Diagram Of Self-Propelled Vibrated Hard Squares, Zhejun Shen
Doctoral Dissertations
In equilibrium, matter condenses into ordered phases due to the combined effects of inter-particle interactions and entropy. In this dissertation, we explore the self-propulsion of particles as an additional nonequilibrium consideration in the mechanisms for ordering. Our experiments employ square-shaped hard particles; in equilibrium, when particle motions are randomly directed, squares form entropically-stabilized phases in which first their orientations, and then their positions, get locked in relative to each other, depending on the density of coverage. When the square tiles are modified to have small propulsion along some body-fixed axis we find that their tendency to order is profoundly altered. …
Pattern Formation And Phase Transition Of Connectivity In Two Dimensions, Arman Mohseni Kabir
Pattern Formation And Phase Transition Of Connectivity In Two Dimensions, Arman Mohseni Kabir
Doctoral Dissertations
This dissertation is devoted to the study and analysis of different types of emergent behavior in physical systems. Emergence is a phenomenon that has fascinated researchers from various fields of science and engineering. From the emergence of global pandemics to the formation of reaction-diffusion patterns, the main feature that connects all these diverse systems is the appearance of a complex global structure as a result of collective interactions of simple underlying components. This dissertation will focus on two types of emergence in physical systems: emergence of long-range connectivity in networks and emergence and analysis of complex patterns. The most prominent …
An Experimental Study Of Lipid-Membrane Based Structure Formation And Development Of A Responsive System, Rui Cao
Doctoral Dissertations
This thesis shows how controlling adhesive interactions among lipid bilayer vesicles and surrounding polymers or particles leads to formation of new mesoscopic and macroscopic structures. The vesicle-gel reported could find application as a closed-cell, 99% water solid platform for releasing cargo in response to a stimulus, either by tuning membrane permeability or by disruption of the vesicles.
Population Annealing: Analysis, Optimization And Application To Glassy Systems, Christopher A. Amey
Population Annealing: Analysis, Optimization And Application To Glassy Systems, Christopher A. Amey
Doctoral Dissertations
Glasses are physical systems that lack structural order and exhibit extremely slow dynamics, which makes them challenging to study. In this thesis we apply Monte Carlo methods to two distinct glassy systems: the 3D Edwards-Anderson spin glass and a binary hard sphere fluid. While significant progress has been made on theoretical and experimental fronts, much of our current understanding of glasses has come from numerical simulations. Standard Monte Carlo techniques cannot be used to perform equilibrium simulations due to slow dynamics in the glassy regime. As a result, several specialized techniques have been developed in order to simulate such systems, …
Transitions Between Radial And Bipolar Liquid Crystal Drops In The Presence Of Novel Surfactants, Jake Shechter
Transitions Between Radial And Bipolar Liquid Crystal Drops In The Presence Of Novel Surfactants, Jake Shechter
Doctoral Dissertations
Liquid crystals (LCs) are a class of molecules that form a variety of configurations easily influenced by external interactions. Of particular interest are rod-like LC molecules confined to a spherical geometry, which have a competition between interfacial tension and elastic deformations. The configuration of the liquid crystal inside a droplet can be controlled using surfactants, influencing the boundary conditions, in an oil-in-water emulsion. I tested the effects of novel surfactants on the configuration of the LC droplets. These novel surfactant molecules, synthesized by collaborators, are oligomers with either a variable length hydrophobic domain or protein sensitive hydrophilic domain. I tested …
Kinetics Of The Crystal-Melt Phase Transformation In Semicrystalline Polymers, Kiran Subramaniam Iyer
Kinetics Of The Crystal-Melt Phase Transformation In Semicrystalline Polymers, Kiran Subramaniam Iyer
Doctoral Dissertations
The assembly of long-chain polymers into an ordered state is a process that has puzzled polymer scientists for several decades. A process that is largely controlled by the strength of intermolecular attractions in small molecular systems, this crystallization in the case of polymers is controlled by a competition between the aforementioned force of attraction between monomers and the formidable conformational entropy of polymer chains. Any factor that affects this conformational entropy, whether that is an equilibrium thermodynamic factor or a kinetic factor, has the ability to control polymer crystallization. In this thesis, we focus on understanding the underlying kinetic processes …
Extreme Dynamics Of Nanomaterials Under High-Rate Mechanical Stimuli, Wanting Xie
Extreme Dynamics Of Nanomaterials Under High-Rate Mechanical Stimuli, Wanting Xie
Doctoral Dissertations
Nanomaterials demonstrate novel mechanical properties attributed to the extremely large interfacial area. At quasi-static rates, the interfacial interactions are crucial in mechanical behaviors, however, materials under extreme mechanical stimuli are rarely studied at nanoscale. With an advanced laser-induced projectile impact test, we perform supersonic impact of micro-projectiles on polymer films, multilayer graphene, carbon- based nanocomposites membranes as well as individual micro-fibers, to study the interface interactions in the high-rate regime, and develop a simplified model to characterize the ballistic performance of materials.
Modeling And Simulation Of Driven Nanopatterning Of Bulk-Material And Thin-Film Surfaces, Ashish Kumar
Modeling And Simulation Of Driven Nanopatterning Of Bulk-Material And Thin-Film Surfaces, Ashish Kumar
Doctoral Dissertations
Material nanostructures such as nanowires, quantum dots, and nanorings have a wide variety of applications in electronic and photonic devices among numerous others. Assembling uniformly arranged and consistently sized nanostructure patterns on solid material surfaces is a major challenge for nanotechnology. This dissertation focuses on developing predictive models capable of simulation and analysis of such nanopattern formation on bulk material and strained thin film surfaces. Single-layer atomic clusters (islands) of sizes larger than a critical size on crystalline conducting substrates undergo morphological instabilities when driven by an externally applied electric field or thermal gradient. We have conducted a systematic and …
Polymeric Impulsive Actuation Mechanisms: Development, Characterization, And Modeling, Yongjin Kim
Polymeric Impulsive Actuation Mechanisms: Development, Characterization, And Modeling, Yongjin Kim
Doctoral Dissertations
Recent advances in the field of biomedical and life-sciences are increasingly demanding more life-like actuation with higher degrees of freedom in motion at small scales. Many researchers have developed various solutions to satisfy these emerging requirements. In many cases, new solutions are made possible with the development of novel polymeric actuators. Advances in polymeric actuation not only addressed problems concerning low degree of freedom in motion, large system size, and bio-incompatibility associated with conventional actuators, but also led to the discovery of novel applications, which were previously unattainable with conventional engineered systems. This dissertation focuses on developing novel actuation mechanisms …
Designing Ion-Containing Polymers With Controlled Structure And Dynamics, Joshua Enokida
Designing Ion-Containing Polymers With Controlled Structure And Dynamics, Joshua Enokida
Doctoral Dissertations
Ion-containing polymers are a unique class of materials for which strong electrostatic interactions dictate physical properties. By altering molecular parameters, such as the backbone chemical structure, the ion content, and the ion-pair identity, the structure and dynamics of these polymers can be altered. Further investigation of the molecular parameters that govern their structure-property relationships is critical for the future development of these polymeric materials. Particularly, the incorporation of ammonium-based counterions into these polymers offers a facile method to tune their electrostatic interactions and hydrophobicity. Applying this concept, a bulky dimethyloctylammonium (DMOA) counterion was used to modify the organic solubility of …
Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu
Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu
Doctoral Dissertations
Oxygen vacancy and ion dynamics in functional oxides are critical factors influencing electrical conductivity and electrochemical activity of oxides assemblies. The recent advancements in deposition and fabrication of oxide heterostructured films with atomic-level precision has led to discovery of intriguing physical properties and new artificial materials. While still under debate, researchers most often attribute these observed behaviors to unique oxygen vacancy distributions in the substrate near heterointerfaces. In electroactive oxides devices such as solid oxide cells (SOCs), oxygen vacancy and ion transport at the triple-phase boundary determines the performance of the device. This complex process motivates numerous remaining questions regarding …
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Doctoral Dissertations
Layered transition metal dichalcogenides (TMDCs) have attracted great interests in recent years due to their physical properties manifested in different polytypes: Hexagonal(H)-TMDC,which is semiconducting, exhibits strong Coulomb interaction and intriguing valleytronic properties; distorted octahedral(T’)-TMDC,which is semi-metallic, is predicted to exhibit rich nontrivial topological physics. In this dissertation,we employ the polarization-resolved micron-Raman/PL spectroscopy to investigate the optical properties of the atomic layer of several polytypes of TMDC. In the first part for polarization-resolved Raman spectroscopy, we study the lattice vibration of both H and T’-TMDC, providing a thorough understanding of the polymorphism of TMDCs. We demonstrate that Raman spectroscopy is a …
Characterization And Manipulation Of The Magnetization Of Nano-Scale Magnetic Structures, Wenming Ju
Characterization And Manipulation Of The Magnetization Of Nano-Scale Magnetic Structures, Wenming Ju
Doctoral Dissertations
Nano-scale magnetic patterned structures and thin films have attracted attention over the past few years due to their unique magnetization distribution and promising application in nonvolatile data storage, magnetic field sensors and spintronic devices. Magnetization states and their switching processes are fundamental investigation subjects of such magnetic systems. This dissertation discusses experimental work and theoretical analysis on investigating the magnetization of these nano-scale magnetic structures and how we can characterize and manipulate the magnetization in order to realize industrial application. The efforts done in this dissertation can be grouped into three topics: First, we focus on whether we can reverse …
Quantum Phase Transitions In Disordered Boson Systems, Zhiyuan Yao
Quantum Phase Transitions In Disordered Boson Systems, Zhiyuan Yao
Doctoral Dissertations
In this dissertation, we study the superfluid-insulator quantum phase transition in disordered boson systems. Recently, there has been considerable controversy over the validity of the scaling relations of the superfluid--Bose-glass quantum phase transition in three dimensions. Results from experimental and numerical studies on disordered quantum magnets contradict the scaling relations and the associated conventional scaling hypothesis for the singular part of the free energy. We determine various critical exponents of the superfluid--Bose-glass quantum phase transition in three-dimensional disordered Bose-Hubbard model through extensive Monte Carlo simulations. Our numerical study shows the previous studies on disordered quantum magnets were performed outside the …
Geometry, Growth And Pattern Formation In Thin Elastic Structures, Salem Al-Mosleh
Geometry, Growth And Pattern Formation In Thin Elastic Structures, Salem Al-Mosleh
Doctoral Dissertations
Thin shells are abundant in nature and industry, from atomic to planetary scales. The mechanical behavior of a thin shell depends crucially on its geometry and embedding in 3 dimensions (3D). In fact, the behavior of extremely thin shells becomes scale independent and only depends on geometry. That is why the crumpling of graphene will have similarities to the crumpling of paper. In this thesis, we start by discussing the static behavior of thin shells, highlighting the role of asymptotic curves (curves with zero normal curvature) in determining the possible deformations and in controlling the folding patterns. In particular, we …
Computational Modeling Of Defect-Engineered Graphene Derivatives And Graphene-Polymer Nanocomposites, Asanka Weerasinghe
Computational Modeling Of Defect-Engineered Graphene Derivatives And Graphene-Polymer Nanocomposites, Asanka Weerasinghe
Doctoral Dissertations
Graphene has unique mechanical, electronic, and thermal properties, which enable a broad range of technological applications. For example, graphene flakes can be used as filler to enhance the properties of polymer-matrix nanocomposites and graphene derivatives, generated by defect engineering and chemical functionalization of single-layer graphene, have tunable properties that are very promising for engineering electronic and thermomechanical metamaterials. A fundamental understanding of the structure-property relationships that govern the function of such nanocomposites and graphene derivatives is required for designing and developing future graphene-based metamaterials. Toward this end, we have conducted a systematic study based on extensive molecular-dynamics simulations of mechanical …
Combined Spectroscopic And Scanning Probe Studies Of Electronic Interactions In Nanostructured 1d And 2d Semiconductors, Peijian Wang
Combined Spectroscopic And Scanning Probe Studies Of Electronic Interactions In Nanostructured 1d And 2d Semiconductors, Peijian Wang
Doctoral Dissertations
This dissertation includes the exploration about the following research questions: 1. What is the correlation between the work function and ground state interactions in organic semiconductor assemblies? 2. How do non-covalent chemical doping tune the work function in MoS2? 3. Are there surface charges in the Aluminum doped ZnO nanocrystals (AZO) and what's the evolution of the surface charges and polarizabilities from undoped AZO to doped AZO? 4. How is the homogeneity like during doping in the organic thermoelectric materials? The techniques we employed in the research is the spatially registered Kelvin Probe Force Microscopy and Photoluminescence spectroscopy …
Antenna Enhanced Graphene Terahertz Emitter And Detector, And Graphene Microwave Detector, Jiayue Tong
Antenna Enhanced Graphene Terahertz Emitter And Detector, And Graphene Microwave Detector, Jiayue Tong
Doctoral Dissertations
Graphene is a promising candidate for optoelectronic and fast electronics research. In THz and sub-THz frequency regime, sensitive detectors are very difficult to make. This dissertation presents my Ph.D study of THz sources and THz/Microwave (MW) detectors made with graphene. My work demonstrates the emission and detection of 1.9 THz radiation from graphene coupled to a double-patch antenna and a silicon lens. More than 3 orders of magnitude performance improvements are achieved in a half-edge-contacted graphene thermoelectric (TE) detector operating at 1.9 THz by antenna coupling and Si lens coupling. The thermoelectric mechanism is also employed in MW detection. A …
Complex Ground States Of Vortices And Filaments, Qingyou Meng
Complex Ground States Of Vortices And Filaments, Qingyou Meng
Doctoral Dissertations
This dissertation consists of two parts. In the first part, we studied the ground state configurations of vortices with multi-scale inter-vortex interactions in layered superconductors. We found that by tuning the multi-scale interaction length, we could create vortex lattice ground states with different symmetries. It has been proposed that these structures can trap ultra-cold atoms for use in quantum emulators. In further work, we measured the phase diagram and discovered many new phases by changing the relative magnitude of the interaction ranges. In the second part, we analyzed the ground state configurations of confined filaments with long-range repulsive interactions. We …
First-Principle Approaches To Strongly Correlated Quantum Spin Systems, Yuan Huang
First-Principle Approaches To Strongly Correlated Quantum Spin Systems, Yuan Huang
Doctoral Dissertations
My Ph.D. research focuses on the numerical study of two quantum spin systems, one is the square-lattice Heisenberg antiferromagnet with ring-exchange interaction at the Neel to valence-bond solid state transition, which is proposed to be described by the theory of deconfined criticality; the other is the highly frustrated pyrochlore Heisenberg antiferromagnet. Both systems are known as prototypical candidates for the exotic spin-liquid state with emergent fractionalized excitations and gauge structure. Regarding the long standing controversy of deconfined criticality, our results conclude that the deconfined critical theory capture the essence of the Neel to valence-bond solid state transition at least at …
Emergent Phenomena In Quantum Critical Systems, Kun Chen
Emergent Phenomena In Quantum Critical Systems, Kun Chen
Doctoral Dissertations
A quantum critical point (QCP) is a point in the phase diagram of quantum matter where a continuous phase transition takes place at zero temperature. Low-dimensional quantum critical systems are strongly correlated, therefore hosting nontrivial emergent phenomena. In this thesis, we first address two decades-old problems on quantum critical dynamics. We then reveal two novel emergent phenomena of quantum critical impurity problems. In the first part of the thesis, we address the linear response dynamics of the $(2+1)$-dimensional $O(2)$ quantum critical universality class, which can be realized in the ultracold bosonic system near the superfluid (SF) to Mott insulator (MI) …
Vibrated Squares As Equilibrium And Active Matter, Lee Askew Walsh
Vibrated Squares As Equilibrium And Active Matter, Lee Askew Walsh
Doctoral Dissertations
We study the effects of particle shape and self-propulsion on the collective behaviors of a two-dimensional granular fluid, using an experimental system of hard square grains. We energize the system by vibration, which, depending on particle shape, induces either isotropic diffusion or persistent self-propulsion in the particles. We use specially designed grains as a model system to study (i) the equilibrium packing of hard squares in two dimensions, (ii) the dynamics of athermal self-propelled particles, and (iii) the melting kinetics of an unconfined granular crystallite. The first study concerns the phase diagram of a two-dimensional fluid of hard squares, which …