Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session F11: Undergraduate Research VIUndergrad Friendly
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Sponsoring Units: APS/SPS Chair: Alexis Knaub, Michigan State Univ Room: 110 |
Tuesday, March 3, 2020 8:00AM - 8:12AM |
F11.00001: Measuring the Glass Transition in Dense 2D Colloidal Fluids William Moore, Orrin Shindell We use Total Internal Reflection Fluorescence Microscopy (TIRF) to analyze dense colloidal fluids fully restricted to two dimensions near their glass transition. Our experiments use 40-100 nm diameter phospholipid vesicles (nanospheres) produced in the lab and commercially manufactured 500 nm and 1000 nm diameter fluorescent polystyrene spheres (microspheres). The microspheres are individually resolvable under TIRF, which allows us to measure their instantaneous positions in both a fluid and a glass state. For both the nanospheres and the microspheres, the position of the colloidal particles is tracked as a function of time, which allows us to measure the viscosity of the colloidal fluid at a range of particle densities. We are thus able to obtain both structural and dynamical information about two-dimensional dense fluids near their glass transition. |
Tuesday, March 3, 2020 8:12AM - 8:24AM |
F11.00002: Minimum flow rate in electro-coflow Benjamin Overlie, Josefa Guerrero Millan Controlled generation of micron and sub-micron sized drops continues to be of strong interest for the scientific community due to the variety of applications in many different fields. Emulsion drops can be generated by flowing two immiscible liquids inside a glass-based microfluidic device. Their minimum size will be of the order of the tip size. To create smaller drops, an external electric field can be used, similarly to what it is done in the classical electrospray. In electrospray, a liquid is issued into air from an electrified needle. When the flow rate of the liquid is controlled, there is a minimum flow rate below which a cone-jet cannot be formed regardless of the applied voltage. This minimum flow rate gives you the minimum drop size that can be generated, usually one or two orders of magnitude smaller than the tip size. We explore this lower limit in electro-coflow using pressure control instead, and we have found a different result than in electrospray, with a more complex behavior. The use of pressure control and the presence of an outer moving fluid, enrich the dynamics in the minimum flow rate limit. |
Tuesday, March 3, 2020 8:24AM - 8:36AM |
F11.00003: Energy spectra for turbulent Rayleigh-Bénard convection Michael Kwan, Janet D Scheel We investigated the scaling behaviors for numerically simulated, turbulent Rayleigh-Bénard convection by determining the kinetic and thermal energy spectra. The systems have aspect ratio 1, Prandtl numbers 0.7, 0.021 and 0.005, and various Rayleigh numbers ranging from 105 to 1010. Whereas in previous studies the frequency spectra from a time series were considered, we calculated the energy spectra from spatial fields. In particular, we performed Fourier analysis on two-dimensional cross sections of the temperature and velocity fields. We also computed the velocity and temperature structure functions on the same cross sections to verify our findings. Lastly, we tested whether Kolmogorov's 1941 (K41) scaling law or the Bolgiano-Obukhov (BO) scaling law applied to both the kinetic and thermal energy spectra for the various systems. |
Tuesday, March 3, 2020 8:36AM - 8:48AM |
F11.00004: The Effect of Short Range Attractions on Sequence Defined Polyelectrolyte Coacervation Natalia Markiewicz, Tyler Lytle, Charles Sing Complex coacervation is the liquid-liquid phase separation of polyelectrolytes in aqueous salt solution into a polymer-dense phase, the coacervate, and a polymer-dilute phase, the supernatant. Previous work using Monte Carlo simulations demonstrated that changing the sequence of charged and neutral monomers on polyelectrolytes while keeping the charge fraction constant alters the extent of phase separation. However, previous data does not account for the hydrophobicity of different neutral monomers. To understand the coacervation of polymers with various chemical structures, van der Waals interactions at various strengths are included in Monte Carlo simulations to show hydrophobic effects in the system. Comparisons are made to existing Monte Carlo simulations and experimental data. Understanding these patterning effects will enhance the knowledge of biomacromolecule phase separation, as well as expand the understanding of sequence-dependent polymer physics. |
Tuesday, March 3, 2020 8:48AM - 9:00AM |
F11.00005: Measurement of Low Temperature Strain in 3D Printed Materials Joeseph Moore, Michael Ray The versatility and ease of use of 3D printing provides access for custom built parts to be quickly manufactured for experimental applications. However, not much is currently known about the behavior of these materials at low temperatures. In this project we measured the thermal properties of a 3D printed material in a cryogenic environment in order to determine its suitability for use in low temperature applications. Specifically, we used a strain gauge to measure the thermal contraction of Polylactic Acid, which is a common material used in 3D printing. We will present our results and discuss the implications for its use in low temperature experiments. |
Tuesday, March 3, 2020 9:00AM - 9:12AM |
F11.00006: Measurement of the Low Temperature Porosity of 3D Printed Materials Kevin Coan, Michael Ray Over the past decade, 3D printing has become popular due to its ease of manufacturing and low cost. This work will explore the possibility of using 3D printers to design custom components for use in low temperature experiments. Specifically, we designed an experiment to test the low temperature porosity of Polylactic Acid, a common 3D printed material. We will present the methods used in this experiment, the results obtained, and then discuss its implications for low temperature use. |
Tuesday, March 3, 2020 9:12AM - 9:24AM |
F11.00007: Theory of time-resolved optical conductivity of superconductors: comparing two methods for its evaluation John Revelle, Ankit Kumar, Alexander F Kemper Time-resolved optical conductivity is an oft-used tool to interrogate quantum materials driven out of equilibrium. Theoretically calculating this observable is a complex topic with several approaches discussed in the literature. Using a non-equilibrium Keldysh formalism and a functional derivative approach to the conductivity, we present a comparison of two particular approaches to the calculation of the optical conductivity, and their distinguishing features, as applied to a pumped superconductor. The two methods are distinguished by the relative motion of the probe and gate times; either the probe or gate time is kept fixed while the other is swept. We find that both the methods result in same qualitative features of the time-resolved conductivity after pump is over. However, calculating the conductivity by keeping the gate fixed removes artifacts inherent to the other method. We provide software that, based on data for the first method, is able to construct the second approach. |
Tuesday, March 3, 2020 9:24AM - 9:36AM |
F11.00008: Superconductor-based light detection Kyril Kavetsky, Harish Krishnamoorthy, Cesare Soci, Michael Lim The ability to detect a single photon could have powerful applications in high-precision object location and quantum information encryption. A superconducting nanowire single-photon detector (SNSPD) is a promising solution that is smaller than the period at the end of this sentence. While they are commercially available now, there is still some room for improvement of efficiency, particularly when a wider operational bandwidth is required, which could be achieved by improving the light absorption. This research presents finite-element-method-based simulations to enhance the absorption in superconducting thin films by utilizing plasmonic nanostructures with broadband absorption response. |
Tuesday, March 3, 2020 9:36AM - 9:48AM |
F11.00009: Phenomenological description of excitonic complexes in tip-enhanced photoluminescence of 2D materials Zachary Withers, Dmitri Voronine Two dimensional materials exhibit different electronic and optical properties than the corresponding bulk materials. Transition metal dichalcogenides (TMDs) are semiconducting 2D crystals that exhibit unusually strong photoluminescence (PL) signals due to the stability of excitons at room temperature. However, many factors can effect the measured intensity of PL signals including charge doping or the presence of a plasmonic AFM tip. Here we present a set of phenomenological rate equations in order to model the intensity of PL in tip-enhanced experiments involving tip-sample distance dependent measurements and near field imaging. Furthering the understanding of exciton dynamics around heterojunctions of TMDs may lead to the engineering of new optoelectronic devices such as optical transistors, novel optomechanics, and controllable signaling on the nanoscale. |
Tuesday, March 3, 2020 9:48AM - 10:00AM |
F11.00010: Double Resonant Local Fields Appreciably Enhance Third Harmonic Generation in Core-shell Nano-cavity Wenbo Zang, Zhuo Chen, Zhongwei Wang We simulate the intensity of third harmonic generation (THG) in a metallic core-shell nanostructure in double resonant conditions, where the corresponding wavelength of two cavity modes are tuned in to couple with the wavelength of the pump light and the THG signal simultaneously by adjusting the refractive index of the dielectric. It turns out that the double resonant condition is crucial to our discovery. |
Tuesday, March 3, 2020 10:00AM - 10:12AM |
F11.00011: Developing and controlling single-photon emitters by tip-enhanced photoluminescence nanospectroscopy and nano-localized force control Jun Yan, Chuanlin Li, Molly A. May, Tao Jiang, Markus B. Raschke Strain-induced single-photon emitters in two-dimensional (2D) materials associated with deterministically located quantum wells could pave the way for quantum state transfer in solid state qubits. However, far-field optical techniques can neither spatially resolve these highly localized emitters nor allow for deterministic control of the light-matter interaction. Here, we develop plasmonic tip-induced, nano-localized force control to generate, tune, and control nano-localized quantum states in monolayer WSe2 by tuning the strain gradients and the plastic deformation depth with sub-nanometer precision. We investigate exciton funnelling behavior and strain-induced bandgap modification from spectral peak shift and intensity of the indented nanostructures, which could possibly help to reveal the deterministic formation of single-photon quantum emitter. In addition, we provide a perspective on this tip-based nanocavity approach, which has been used to probe in photoluminescence bright and dark exciton emissions, localized states, and interlayer excitons in 2D heterostructures. |
Tuesday, March 3, 2020 10:12AM - 10:24AM |
F11.00012: Velocity, Release and Attack Angle and Distance of an Ultimate Frisbee Disc Andrew Polcari This study is exploring how an ultimate frisbee disc rotates and acts while in flight using high-speed video. The relationship between angular speed and flight stability and optimal release angle and flight distance will be explored. The methods used will all be physical methods as opposed to a re-creation of a computer program. By attaching a disc to a motor and spin it at varying speeds, we will be able to determine the optimal angular velocity and relate those measurements to flight stability. To measure the distance, this project will use a high-speed camera to measure the angle of release and then correlate those data to the distance travelled by that specific throw. The results explore pitch, roll, and velocity. This project will show that physics can be related to any topic and discipline. It relates a sport, hobby and past time all together and shows how physics affects the classic piece of plastic we toss between us. |
Tuesday, March 3, 2020 10:24AM - 10:36AM |
F11.00013: Study on the Apparent Weight of Hourglass Caused by Sand Flow Chunzhen Li Due to the acceleration of the sand centroid, the hourglass's apparent weight will change slightly with time in the process of sand flow, which is the sum of the effects of each part of the sand in the hourglass. By establishing an hourglass model, in this paper we can get the relationship between the centroid position vector of each part of the sand and the time, and then get the time-dependent acceleration of the overall centroid of the sand. According to the shape of the hourglass itself and the parameters of each part, the process of sand flow can be devided into five stages. Then the mismatch between theoretical and experimental values is analyzed, and the imperfect elastic collision between sand and the bottom of the hourglass is used to explain and further revise the previous theory. |
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