Physics Commons^™

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 …

Thermal Conductivity And Mechanical Properties Of Interlayer-Bonded Graphene Bilayers, Afnan Mostafa

Masters Theses

Graphene, an allotrope of carbon, has demonstrated exceptional mechanical, thermal, electronic, and optical properties. Complementary to such innate properties, structural modification through chemical functionalization or defect engineering can significantly enhance the properties and functionality of graphene and its derivatives. Hence, understanding structure-property relationships in graphene-based metamaterials has garnered much attention in recent years. In this thesis, we present molecular dynamics studies aimed at elucidating structure-property relationships that govern the thermomechanical response of interlayer-bonded graphene bilayers.

First, we present a systematic and thorough analysis of thermal transport in interlayer-bonded twisted bilayer graphene (IB-TBG). We find that the introduction of interlayer C-C …

The Fate Of The Crossbridge After Phosphate Rebinding: Implications For Fatigue, Christopher P. Marang

Doctoral Dissertations

In response to repeated intense contractile activity, a muscle’s ability to generate force decreases due to the created state of muscular fatigue. This compromised force production state is dependent on changes within the microenvironment of muscle thought to alter the function of the force generating, contractile protein myosin. For example, phosphate (P_i), elevated during fatigue, has been suggested to alter how myosin generates force. However, the effects of P_i are not straightforward, as muscle fiber data suggest that P_i's interaction with myosin may be force-dependent. In particular, P_i has no effect on maximal shortening …

Design And Fabrication Of A Trapped Ion Quantum Computing Testbed, Christopher A. Caron

Masters Theses

Here we present the design, assembly and successful ion trapping of a room-temperature ion trap system with a custom designed and fabricated surface electrode ion trap, which allows for rapid prototyping of novel trap designs such that new chips can be installed and reach UHV in under 2 days. The system has demonstrated success at trapping and maintaining both single ions and cold crystals of ions. We achieve this by fabricating our own custom surface Paul traps in the UMass Amherst cleanroom facilities, which are then argon ion milled, diced, mounted and wire bonded to an interposer which is placed …

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 …

Parallel Algorithms For Time Dependent Density Functional Theory In Real-Space And Real-Time, James Kestyn

Doctoral Dissertations

Density functional theory (DFT) and time dependent density functional theory (TDDFT) have had great success solving for ground state and excited states properties of molecules, solids and nanostructures. However, these problems are particularly hard to scale. Both the size of the discrete system and the number of needed eigenstates increase with the number of electrons. A complete parallel framework for DFT and TDDFT calculations applied to molecules and nanostructures is presented in this dissertation. This includes the development of custom numerical algorithms for eigenvalue problems and linear systems. New functionality in the FEAST eigenvalue solver presents an additional level of …

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) …

Tunneling Assisted Forbidden Transitions In The Single Molecule Magnet Ni4, Yiming Chen

Doctoral Dissertations

This dissertation presents work in exploring novel quantum phenomena in singlemolecule magnets (SMMs) and superconducting circuits. The degree of the freedom studied is the magnetic moment of a single molecule and the flux quantum trapped in a superconducting ring. These phenomena provide us with new insights into some basic questions of physics and may also find their application in quantum computing. The molecule we studied is Ni4 ([Ni4(hmp)(dmp)Cl]4) which can be treated as a spin-4 magnet. The large magnetic anisotropy of the molecule leads to bistability of the magnetic moment at low temperatures, with spin-up and spin-down states separated by …

Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins

Doctoral Dissertations

Van der Waals (vdW) interactions influence a variety of mesoscale phenomena, such as surface adhesion, friction, and colloid stability, and play increasingly important roles as science seeks to design systems on increasingly smaller length scales. Using the full Lifshitz continuum formulation, this thesis investigates the effects of system materials, shapes, and configurations and presents open-source software to accurately calculate vdW interactions. In the Lifshitz formulation, the microscopic composition of a material is represented by its bulk dielectric response. Small changes in a dielectric response can result in substantial variations in the strength of vdW interactions. However, the relationship between these …

Where To Buy Materials For The Activities, Morton Sternheim

Nanotechnology Teacher Summer Institutes

Sources for some of the less common materials used in the activities.

Gelatin Diffusion Experiment, Jennifer Welborn

Nanotechnology Teacher Summer Institutes

In this activity, nanotech participants will:

- See how food dyes and gelatin are used to model the delivery of nanoscale medicines to cells in the human body - Measure diffusion distances of 3 different colors of food dye by: Eye, photo image on a computer, ADI software (Analyzing Digital Images) Some useful websites:

• http://www.echalk.co.uk/Science/biologyContent.htm Life Processes and Cells
• http://workbench.concord.org/database/activities/321.html Molecular Workbench Database. Diffusion, osmosis, ...

Atomic Force Microscopes, Rob Snyder, Jennifer Welborn

Nanotechnology Teacher Summer Institutes

PowerPoint overview. A student activity that builds an atomic force microscope model.

The Science Of Two Dimensional Materials (Powerpoint), Jun Yan

Nanotechnology Teacher Summer Institutes

Graphene is a single atomic sheet of graphite.

Exercise: how much graphene do we need to cover the surface of the empire state building?

Nanoscale Thin Films, Rob Snyder

Nanotechnology Teacher Summer Institutes

An activity that makes a nanoscale film of oleic acid on water. The student will

• Learn about Ben Franklin’s observations of a thin film that had a nanoscale dimension.

• Create a very thin film with a very dilute solution of oleic acid.

• Use data you collect to determine if you made a thin film with a nanoscale dimension that formed on the surface of water.

• Learn about the molecular interactions that resulted in the formation of the thin film.

• Be introduced to the Big Ideas of Nanoscale Self-Assembly

Seeing At The Nanoscale: New Microscopies For The Life Sciences, Jennifer Ross

Nanotechnology Teacher Summer Institutes

Visualizing single modules with fluorescence microscopy

Ozone, Uv, And Nanoparticles, Morton Sternheim, Jennifer Welborn

Nanotechnology Teacher Summer Institutes

•Ultraviolet light causes skin damage and cancer •Ozone in the stratosphere blocks UV •Sunscreen blocks UV, partly •Nanoparticles in sunscreen improve blocking Sunscreen PowerPoint and activities based on NanoSense web site:

http://nanosense.sri.com/activities/clearsunscreen/index.html

Powers Of Ten: From Meters To Nanometers And Beyond, Rob Snyder

Nanotechnology Teacher Summer Institutes

The goal of this activity is to guide students toward an understanding of nanoscale dimensions by:

• Making a number of measurements using meter sticks, magnifiers, microscopes and spectrometers so students can make observations and generate their own data.

• Using scientific notation to compare the measurements they have made with the dimensions of very small structures

Self Assembly, Mark Tuominem, Jennifer Welborn, Rob Snyder

Nanotechnology Teacher Summer Institutes

No abstract provided.

Magnetic Memory: Data Storage And Nanomagnets, Mark Tuominem

Nanotechnology Teacher Summer Institutes

An overview of magnetic data storage and a simple activity.

Nanomedicine, Mark Tuominen

Nanotechnology Teacher Summer Institutes

An overview of nanomedicine. The end goal of nanomedicine is improved diagnostics, treatment and prevention of disease. Nanotechnology holds key to a number of recent and future breakthroughs in medicine.

A Non-Linear Eigensolver-Based Alternative To Traditional Self-Consistent Electronic Structure Calculation Methods, Brendan E. Gavin

Masters Theses 1911 - February 2014

This thesis presents a means of enhancing the iterative calculation techniques used in electronic structure calculations, particularly Kohn-Sham DFT. Based on the subspace iteration method of the FEAST eigenvalue solving algorithm, this nonlinear FEAST algorithm (NLFEAST) improves the convergence rate of traditional iterative methods and dramatically improves their robustness. A description of the algorithm is given, along with the results of numerical experiments that demonstrate its effectiveness and offer insight into the factors that determine how well it performs.

Making Solar Cells, D. Venkataraman

Nanotechnology Teacher Summer Institutes

Overview of solar energy and photovoltaic cells. Making a cuprous oxide cell activity.

Nanofilters For Clean Water, Morton Sternheim

Nanotechnology Teacher Summer Institutes

•The problem: adequate clean water •Kinds of filters •Desalination of salt water •Cleaning polluted water •Hands on nanofiltration experiment Adapted from the Nanosense project: http://nanosense.sri.com/activities/finefilters/index.html

More On Powers Of Ten, Morton Sternheim

Nanotechnology Teacher Summer Institutes

A powers of ten personation and activity adapted from the Nanosense project:

http://nanosense.sri.com/activities/sizematters/index.html

Synthesize A Nanoscale Ferrofluid, Rob Snyder

Nanotechnology Teacher Summer Institutes

The chemical synthesis of a ferrofluid is a nanoscale science activity that originally appears in the Journal of Chemical Education. Access to the following website requires a subscription to the journal. J. Chem. Educ., 76, 943-948 (1999). The article was authored by Jonathan Breitzer and George Lisensky.