Session F4: Undergraduate Research/Society of Physics Students III

Light: A Spectrum of Utility, the 2014-2015 Society of Physics Students Science Outreach Catalyst Kit

The Science Outreach Catalyst Kit (SOCK) is a set of activities and demonstrations designed to bolster the outreach programs of undergraduate Society of Physics Students (SPS) chapters, creating the framework for a lasting outreach program. Targeted for students ranging from kindergarten to high school, the SOCK allows students to actively engage in hands-on activities that teach them scientific skills and allow them to exercise their natural curiosity. The 2014-2015 SOCK united themes from the 2014 International Year of Crystallography and the 2015 International Year of Light to explore how light is used as a tool every day. This presentation will discuss the contents of the SOCK, which contains a large assortment of materials, such as diffraction glasses, polarizers, ultraviolet flashlights, etc. and describe the research and development of the activities. Each activity explores a different light phenomenon, such as diffraction, polarization, reflection, or fluorescence. These activities will promote critical thinking and analysis of data.   

Capacitively-coupled differential position detection in the development of a high-sensitivity torsion balance

We report on the development of a high-sensitivity torsion balance using a capacitively-coupled Wheatstone Bridge. The torsion balance will be employed to measure the Casimir Force, with a particular emphasis on the surface patch effects that are ubiquitous on metallic surfaces.~We will show that these effects also play a significant role~in another class of experiments involving quantum-point contacts between two metal wires.   

Mapped grid methods for Numerov propagation

The Computational toll of solving the Schroedinger equation for certain atomic systems is sometimes prohibitively heavy. We present a grid-mapping method which decreases the number of points needed, and at the same time maintains or increases accuracy for three-atom scattering. By developing a hyperspherical mapping method for Numerov propagation, scattering cross-sections can be found for a large range of energies. This method is useful for systems with very shallow bound states where the mapping will give a large number of data points inside the potential well while decreasing the number of points at a large hyper-radius. The change in grid sizes is controlled by a mapping function that is easily modified. Results are shown for scattering in the HeH$_{\mathrm{2}}$ and HNe$_{\mathrm{2}}$ systems.   

Simulation of Planetary Formation using Python

A program to simulate planetary formation was developed in the Python programming language. The program consists of randomly placed and massed bodies surrounding a central massive object in order to approximate a protoplanetary disk. The orbits of these bodies are time-stepped, with accelerations, velocities and new positions calculated in each step. Bodies are allowed to merge if their disks intersect. Numerous parameters (orbital distance, masses, number of particles, etc.) were varied in order to optimize the program. The program uses an iterative difference equation approach to solve the equations of motion using a kinematic model. Conservation of energy and angular momentum are not specifically forced, but conservation of momentum is forced during the merging of bodies. The initial program was created in Visual Python (VPython) but the current intention is to allow for higher particle count and faster processing by utilizing PyOpenCl and PyOpenGl. Current results and progress will be reported.   

Effects of Turbulence on Cosmic Ray Propagation in Protostar Systems

The magnetic field associated with young stellar objects are expected to have an hour-glass geometry, i.e. the magnetic field lines are pinched together in the equatorial plane surrounding the forming star but are subsumed smoothly onto a background field at large distances. In such a structure, incoming cosmic rays experience both a funneling effect, which acts to magnify the flux impinging on the circumstellar disk, and a magnetic mirroring effect that acts to reduce that flux. These effects nearly cancel out for simple underlying magnetic field structures with respect to the leading order. However, the environments surrounding young stellar objects are expected to be highly turbulent and, thus, act to complicate these effects. We consider here how the presence of magnetic field fluctuations affects the process of magnetic mirroring, and thereby changes the flux of cosmic rays striking the circumstellar disks. These results may have significant consequences for the ionization fraction of the disk, which in turn dictates the efficiency with which disk material can accrete onto the central object.   

Transverse distortion effects on the Kasteleyn and KDP transition in spin ice

Geometrically frustrated pyrochlore oxides containing a rare-earth ion and a transition metal ion form a network of corner-sharing tetrahedra. Prominent examples include Dy$_{2}$Ti$_{2}$O$_{7}$ and Ho$_{2}$Ti$_{2}$O$_{7}$. Magnetic frustration in these compounds suppresses the formation of a long-range ordered ground state resulting in an exotic phase of matter called spin ice. Elucidating the role of external perturbations such as pressure and magnetic field is an important step towards understanding the novel KDP and Kasteleyn phase transitions arising in these classical spin ice materials. Utilizing an analytical approach based on the Husimi tree approximation, we investigate the effects of both transverse and uniaxial pressure distortion of the spin ice tetrahedra on both the KDP and Kasteleyn transition in the presence of an external magnetic field. Compared to the uniaxial distortion scenario, we find that including the effects of transverse distortion leads to further suppression of magnetization and heat capacity in both the Kasteleyn and KDP cases.   

Super Atomic Molecular Orbitals of Variably Protonated Symmetric Molecules

The molecular structure of symmetric molecules creates conducive conditions for delocalized orbitals. The $\pi$ bonding delocalizes the valence electrons away from the individual molecules. These delocalized valence electrons allow the symmetric molecules to adapt the characteristics analogous to that of an individual atom, creating Super Atomic Molecular Orbitals, SAMOs. The symmetric molecule is then comparable to that of an individual atom with its regular atomic orbitals. When these symmetric molecules are protonated in any form, there are notable changes in the shapes of the Super Atomic Molecular Orbitals. We use the Density Functional Theory with a grid mesh method to compute the wavefunctions of those SAMOs. Then we examine the Rydberg States of these symmetric molecules through the calculated Eigenstates, and find an important trend in the filling of the SAMOs as well as relationships between variably protonated symmetric molecules. This is potentially very useful to understanding the photovoltaic effect in the fullerene- based solar cells.   

Comparative Study of Wavelet Basis Set and Finite-Difference Time-Domain Methods for the Time Propagation of Quantum and Classical Systems

An extensive comparison in error accumulation between a grid point method, in particular finite-difference time-domain (FDTD), and a basis set method using Daubechies wavelets is presented in the modeling of electromagnetic (EM) pulses (classical) in inhomogeneous media and quantum (QM) wavepackets interacting with various potentials. It is demonstrated that the density of wavelet functions needed to attain a certain level of accuracy is far less than needed for grid points (FDTD) translating to savings in computational memory and processing. Since neighboring wavelet basis functions have overlapping support, fictitious wavelet projections created by derivative matching (T.A. Driscoll and B. Fornberg) will be used to handle Dirichlet boundary conditions in both the EM and QM cases in order to prevent rapid error growth.   

Temperature influenced higher order transverse mode in vertical-cavity surface emitting laser

This research discussed the transverse beam profile of VCSEL with variation of ambient temperature. In this experiment, the transverse mode profile presented a broken pattern when ambient temperature kept decreasing. On the other hand, the optical spectrum analyzer showed that the laser output appeared another frequency when the same approach applied. Therefore, an experiment was conducted by using grating in order to observe the separation of beam. The two separate and unstable spots showed on screen 10 meter away, indicating that the different wavelength really emerged in the output of laser. This result contributes to understanding the relationship between temperature modification and the transverse modes of VCSEL.   

Dissipative coherence of a superconducting qubit for microwave detection

Recent progress in coherent control and measurement of superconducting qubits has opened avenues to previously inaccessible regimes of metrology. Here we realize a detection scheme for microwave signals. Our scheme utilizes a superconducting transmon qubit coupled to a three-dimensional cavity. When subjected to a weak drive signal near resonance, the qubit equilibrates to a steady state coherence that arises from the competition between driven and dissipative dynamics. By measuring this steady state coherence with quantum state tomography, we map the quantum state to characteristics of the drive signal with shot noise-limited resolution. We report detection figures of merit and discuss applications to itinerant microwave fields.   

Optimized reconstruction methods for imaging squeezed microwave states

Superconducting parametric amplifiers (paramps) are essential tools for quantum-limited measurement of superconducting qubits. A central feature of these devices is that they can ideally amplify information in one quadrature without adding noise while simultaneously squeezing fluctuations in the orthogonal quadrature. At microwave frequencies, moment-based reconstruction techniques are commonly utilized to image such squeezed states. Motivated by a desire to characterize and improve paramp squeezing performance, we have developed simulations to understand the application of these reconstruction techniques, with a focus on determining their performance at large signal gains where the amplifier output field becomes non-Gaussian. We make comparisons of this analysis to experimental data. We have also developed a complementary imaging method based on deconvolution techniques that is effective for high signal-to-noise ratios. This method benefits from a simple implementation and provides a best estimate for the output field Q function. We discuss experimental implementations of these techniques facilitated by the use of a broadband parametric amplifier.   

Toroidal moment contributions to the multiferroic acoustic susceptibility

We consider the effects of toroidal moment corrections to the acoustic susceptibility tensor of a material that is simultaneously ferroelectric and a canted antiferromagnet (multiferroic). Using the Landau-Lifshitz equation of motion for the magnetization, the Landau-Khalatnikov relaxation equation for the electric polarization, and an equation of motion for the toroidal moment we analytically compute the corrections to the acoustic susceptibility tensor. In the presence of toroidal moment coupling we find that the previously vanishing susceptibility components in the multiferroic channel are now non-zero. Additionally, the toroidal corrections give rise to nonzero, asymmetric susceptibility components in the magnetic, electric, and multiferroic channels with both real and imaginary corrections to the susceptibility.