Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session C12: Undergraduate Research/SPS IIIFocus Undergraduate
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Sponsoring Units: SPS FED Chair: Brad Conrad, Society of Physics Students Room: 271 |
Monday, March 13, 2017 2:30PM - 3:06PM |
C12.00001: Making the forbidden allowed: new approaches to light emission Invited Speaker: Nicholas Rivera Quantum electrodynamics (QED) is arguably one of the most successful theories of physics. In the early twentieth century, it was developed in order to provide a basic framework for light-matter interactions. Considering the fact that today is almost 90 years since Dirac's first paper on QED, it may seem surprising that there are still unexplored consequences for the physics of light-matter interaction. It has long been known that the diversity of light-matter interactions accessible to a system seems fundamentally limited by the small size of an atom relative to the wavelength of the light it emits, as well as by the small value of the fine-structure constant. In this talk, we'll discuss how polaritons in recently emerging materials can relax these restrictions on light-matter interaction. We developed a general theory of light-matter interactions [10.1126/science.aaf6308] with two-dimensional systems like graphene supporting plasmon polaritons. These plasmons effectively make the fine-structure constant larger and bridge the size gap between atoms and light. This theory reveals that conventionally forbidden light-matter interactions such as extremely high order multipolar transitions, two-plasmon spontaneous emission, and singlet-triplet phosphorescence processes can occur on very short time scales comparable to those of conventionally fast transitions. Showing a means to access these transitions at very fast rates, we move on to discuss two schemes by which forbidden transitions can be made dominant over allowed transitions. In the first scheme, we imbue polaritons with angular momentum, changing the selection rules for both single-polariton and multipolariton transitions. In the second scheme, we take advantage of the narrow Reststrahlen bands of polar dielectrics to selectively enhance slow transitions like two-photon spontaneous emission processes to the point where they dominate over all other decay mechanisms. [Preview Abstract] |
Monday, March 13, 2017 3:06PM - 3:18PM |
C12.00002: My Summer with Science Policy Marissa Murray This past summer I interned at the American Institute of Physics and helped research and write articles for the FYI Science Policy Bulletin. FYI is an objective digest of science policy developments in Washington, D.C. that impact the greater physical sciences community. Over the course of the summer, I independently attended, analyzed, and reported on a variety of science, technology, and funding related events including congressional hearings, government agency advisory committee meetings, and scientific society events. I wrote and co-wrote three articles on basic energy research legislation, the National Institute of Standards and Technology improvement act, and the National Science Foundation's big ideas for future investment. I had the opportunity to examine some challenging questions such as what is the role of government in funding applied research? How should science priorities be set? What is the right balance of funding across different agencies and programs? I learned about how science policy is a two-way street: science is used to inform policy decisions and policy is made to fund and regulate the conduct of science. I will conclude with how my summer working with FYI showed me the importance of science advocacy, being informed, and voting. [Preview Abstract] |
Monday, March 13, 2017 3:18PM - 3:30PM |
C12.00003: Efficiencies of Dye-Sensitized Solar Cells using Ferritin-Encapsulated Quantum Dots with Various Staining Methods Luis Perez Dye-sensitized solar cells (DSSC) have the potential to replace traditional and cost-inefficient crystalline silicon or ruthenium solar cells. This can only be accomplished by optimizing DSSC's energy efficiency. One of the major components in a dye-sensitized solar cell is the porous layer of titanium dioxide. This layer is coated with a molecular dye that absorbs sunlight. The research conducted for this paper focuses on the different methods used to dye the porous TiO2 layer with ferritin-encapsulated quantum dots. Multiple anodes were dyed using a method known as SILAR which involves deposition through alternate immersion in two different solutions. The efficiencies of DSSCs with ferritin-encapsulated lead sulfide dye deposited using SILAR were subsequently compared against the efficiencies produced by cells using the traditional immersion method. It was concluded that both methods resulted in similar efficiencies (?$\approx $.074{\%}); however, the SILAR method dyed the TiO2 coating significantly faster than the immersion method. On a related note, our experiments concluded that conducting 2 SILAR cycles yields the highest possible efficiency for this particular binding method. [Preview Abstract] |
Monday, March 13, 2017 3:30PM - 3:42PM |
C12.00004: Delaminated Transfer of CVD Graphene Alexis Clavijo, Jinhai Mao, Nikhil Tilak, Michael Altvater, Eva Andrei Single layer graphene is commonly synthesized by dissociation of a carbonaceous gas at high temperatures in the presence of a metallic catalyst in a process known as Chemical Vapor Deposition or CVD. Although it is possible to achieve high quality graphene by CVD, the standard transfer technique of etching away the metallic catalyst is wasteful and jeopardizes the quality of the graphene film by contamination from etchants. Thus, development of a clean transfer technique and preservation of the parent substrate remain prominent hurdles to overcome. In this study, we employ a copper pretreatment technique and optimized parameters for growth of high quality single layer graphene at atmospheric pressure. We address the transfer challenge by utilizing the adhesive properties between a polymer film and graphene to achieve etchant-free transfer of graphene films from a copper substrate. Based on this concept we developed a technique for dry delamination and transferring of graphene to hexagonal boron nitride substrates, which produced high quality graphene films while at the same time preserving the integrity of the copper catalyst for reuse. [Preview Abstract] |
Monday, March 13, 2017 3:42PM - 3:54PM |
C12.00005: Scalable growth and characterization of monolayer WSe$_{2}$ Frank McKay, Matt Seitz, Matthew Adams, Paul Nguyen, Jennifer Heath, David Cobden 2D materials such as monolayer WSe$_{2}$ have unique optoelectronic properties which enable the manufacture of new types of devices. To create monolayer films, typically, WSe$_{2}$ is mechanically exfoliated using adhesive tape, which is not a scalable approach. To address this problem we use physical vapor deposition to deposit films. We insert a secondary heating coil into our furnace that allows us to create two temperature zones that are both separately tunable and locally uniform. By separately controlling the source and substrate temperatures we produce single, more uniform, larger 2D crystals of up to 15 microns. We have prepared field-effect transistors using both grown and exfoliated WSe$_{2}$ crystals, allowing the electronic quality to be compared. [Preview Abstract] |
Monday, March 13, 2017 3:54PM - 4:06PM |
C12.00006: Tuning Magnetic Proximity Effect in Pt\textbar CoFe$_{2}$O$_{4}$ Bilayers by Controlling Interface Structure Adam Goad, Igor Pinchuk, Walid Amamou, Roland Kawakami With our project, we are looking to report evidence of tuned magnetism in a thin film of Pt covering a ferromagnetic insulator, CoFe$_{2}$O$_{4}$. ~Hall bars are created to enable us to make Hall measurements of the induced magnetic Pt thin film. ~If anomalous hall effect is present in the Pt thin film, evident of magnetic proximity effect, then we see a non-linear relationship between the measured Hall voltage and the applied magnetic field. ~We have confirmed the presence of magnetic proximity effect in the Pt thin film and have engaged in tuning the effect. ~By using an alternating shutter method of molecular beam epitaxial growth, we can determine the termination layer of the interface. Alternating shutter method has allowed for the first demonstration of interface structure influence on magnetic proximity effect. If we can verify interface structure influence on magnetic proximity effect in thin films, then we can pursue verification of interface structure influence in two-dimensional (2D) materials. ~The possibilities of 2D materials are bountiful, but if we are able to exhibit magnetic proximity effect and interface structure influence in them, we can unlock the possibilities of 2D materials. [Preview Abstract] |
Monday, March 13, 2017 4:06PM - 4:18PM |
C12.00007: Modelling sodium cobaltate by mapping onto magnetic Ising model Patrick Gemperline, David Jonathan Pryce Morris Fast Ion conductors are a class of crystals that are frequently used as battery materials, especially in smart phones, laptops, and other portable devices. Sodium Cobalt Oxide, Na$_{x}$CoO$_{2}$, falls into this class of crystals, but is unique because it possesses the ability to act as a thermoelectric material and a superconductor at different concentrations of Na$^{+}$. The crystal lattice is mapped onto an Ising Magnetic Spin model and a Monte-Carol Simulation is used to find the most energetically favorable configuration of spins. This spin configuration is mapped back to the crystal lattice resulting in the most stable crystal structure of Sodium Cobalt Oxide at various concentrations. Knowing the atomic structures of the crystals will aid in the research of the material’s capabilities and the possible uses of the material commercially. [Preview Abstract] |
Monday, March 13, 2017 4:18PM - 4:30PM |
C12.00008: Multiple Spectroscopic Techniques Simultaneously Observe Native and Mutated Protein Unfolding of Horse Heart Cytochrome c Mario Cribari, Brennan Cull, Justin J. Link Understanding of how a protein folds is a topic that has been plaguing various scientific fields for decades. Proper folding is integral to a protein's function, and so knowledge of that folding is pertinent for medical conditions involving malfunctioning proteins, among other things. Some understanding of protein folding can be gained by analyzing the denaturation of a model protein through spectroscopic techniques; specifically, circular dichroism (CD), absorbance, and fluorescence. Wild-type and 13 mutant versions of the model protein horse heart cytochrome c in the oxidized form were analyzed using these techniques. By mutating the protein such that the single fluorescent amino acid tryptophan was present in different regions of the protein, specific information about each region and its folding process was acquired. Combining the information of each region allowed for the development of a global picture of the protein folding, including a possible ordering of the folding of each region. Further analysis about the characteristics of the various regions of the protein and the order in which they fold can allow for a deeper understanding of the protein folding of horse heart cytochrome c. [Preview Abstract] |
Monday, March 13, 2017 4:30PM - 4:42PM |
C12.00009: Design and Fabrication of Novel Polymeric Thin Film Micro-Optical Ring Resonators By Thermocapillary Patterning Yanbing Zhu, Kevin Fiedler, Chengzhe Zhou, Sandra Troian Many interesting physical phenomena at the micro or nanoscale derive from the competition between forces which act exclusively at an interface separating two media such as air and liquid. In particular, we have been exploring a nanofilm patterning technique that exploits the opposition between thermocapillary and capillary forces to form desired 3D shapes which then solidify in situ. In this talk, we describe efforts to fabricate micro-optical ring resonators by projecting thermal distributions onto the surface of a molten polymer film. These distributions are imposed by thermal conduction from patterned preforms on a chilled sapphire window placed in close proximity to the film surface. This non-contact, single-step fabrication process results in solidified shapes whose ultra smooth surfaces minimize scattering losses. While both linear and ring-like waveguides have been fabricated successfully, attempts to conjoin two such elements has been compromised by proximal fluid effects. We describe results of finite element simulations used to overcome this challenge and fabricate optimal shapes. [Preview Abstract] |
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