2018 Summer REU

Summer Research Experience for Undergraduates 2018

2018 Summer REU Student Information & Research Abstracts

Name: Jesus Alvarez

Undergraduate Institution: Pacific University, Oregon

Major: Chemistry

REU Advisor: Rolando Valdés Aguilar

Project Title: Rotational anisotropy second harmonic generation for broken bulk inversion symmetry detection

Abstract: “Second harmonic generation (SHG) is well known as a tool for probing the surface structure of nonlinear optical materials. When a coherent light source of frequency ω1 is incident upon certain materials, the light reflected from the material is twice the frequency, ω2, of the incident beam. Due to its selectivity for non-centrosymmetric materials, second harmonic generation was recently able to be used in identifying the breaking of inversion symmetry in the bulk of Cd2Re2O7. Through the use of this technique a previously unknown electronic phase transition was discovered to be the cause of the broken parity in this material. This presents an interesting way in which the use of nonlinear optical techniques allows the inference of the material’s functional properties from its structural symmetry. Here we present an optical scheme for second harmonic generation that was designed for the testing of novel materials to determine their electronic properties. We performed testing of the optical setup using a sample of GaAs, a well-known non-centrosymmetric semiconductor, and find an interesting angular dependence of the second harmonic signal. In addition to this, we will present data on measurements performed on single crystals of FeGe and Cd2Re2O7.”

Jesus Alvarez Paper

Name: Stephen Gant

Undergraduate Institution: TheOhio State University

Major: Physics

REU Advisor: Jay Gupta

Project Title: 2D material modeling with Density Functional Theory: Applications in scanning tunneling microscopy

Abstract: “This project aims to develop DFT modeling techniques for use in STM analysis. By simulating Ir(111) and Fe/Ir(111)—for which experimental data already exist in-lab—an analysis of the effectiveness of current techniques in DFT is performed.
The techniques are capable of modeling the basic behavior of Ir(111). They accurately
reproduce surface relaxation spacing and topography, while producing a somewhat
accurate LDOS. Band structure calculations also appear normal. Fe/Ir(111) calculations
also appear promising in the aforementioned areas, with the exception of the LDOS for which no viable experimental data exist for comparison. Overall, this project has aided the development of proficient DFT modeling in the group’s arsenal of analytic tools.”

Stephen Gant Paper

Name: Morgan Hamilton

Undergraduate Institution: University of Mount Union

Major: Physics and Mathematics

REU Advisor: Chris Hammel

Project Title: Quantifying nitrogen-vacancy center density in diamond using magnetic resonance

Abstract: “Biologists have recently begun to use nanodiamonds as bright, florescent biomarkers. Florescence originates in transitions between the atomic-like, electronic energy levels of nitrogen-vacancy (NV) defects, composed of a nitrogen substitution adjacent to a carbon lattice vacancy. Engineering brighter nanodiamonds generally requires higher concentrations of NV centers, but quantifying these concentrations via optical measurements alone is prone to complications from surface termination, other defect concentrations, nanodiamond size, etc. Here, we aim to quantify NV densities from the intensity of their zero-field magnetic resonance absorption, centered at 2.87 GHz. To this end we designed and characterized a tunable microwave cavity. For given cavity dimensions, Mathematica code was developed to visualize the resonant modes and calculate their resonant frequencies. From this a magnetic resonance cavity could be designed, and it was demonstrated that the measured resonance frequency matches the theoretical value very well as a function of the cavity length. Coupling from a coaxial microwave line to the cavity was enabled using a loop antenna. By modifying the inductance of the loop, the quality factor of the cavity was enhanced by a factor of three. We thus demonstrated a tunable microwave cavity that can be made to resonate with NV spins. Future work will involve incorporating the cavity in a magnet to measure the microwave absorption amplitude.”

Morgan Hamilton Paper

Name: Jarryd Horn

Undergraduate Institution: Northern Michigan University

Major: Physics and Mathematics

REU Advisor: Fengyuan Yang

Project Title: Epitaxial growth of double perovskite thin films

Abstract: “Here, I report on the preparation and characterization of epitaxial thin films of the doubleperovskite Sr2CrWO6 and Sr2CrReO6 by Ultrahigh Vacuum Magnetron Sputtering. These films were grown on SrTiO3 and LSAT substrates as an efficient way to tune the growth conditions of these film. In the case of Sr2CrWO6, a sputtering powder was synthesized for use as sputtering target. Purity of target powder was confirmed via Powder X-Ray Diffraction and phase purity of epitaxially grown thin films were confirmed by Thin Film X-Ray Diffraction.”

Jarryd Horn Paper

Name: Jordyn Hunter

Undergraduate Institution: Purdue University

Major: Chemical Engineering

REU Advisor: Wolfgang Windl

 

Project Title: Existence of robust edge states in functionalized germanene and stanene nanoribbons

Abstract: “Since the discovery of the quantum spin hall effect, there has been an increase in research in the field of 2D topological insulators, specifically in identifying and developing materials that exhibit the robust edge states characteristic of this topologically distinct state. Density functional theory calculations were performed to study the electronic properties of various functionalized germanene and stanene nanoribbons to identify potential topological insulators through the analysis of band structures and density diagrams. Band structure calculations show an opening of the band gap in GeI and SnI bulk structures with the inclusion of spin-orbit coupling, while GeNH2 does not exhibit this property. The GeI and SnI nanoribbon band
structures show further evidence of edges states, while the GeNH2 nanoribbon structures do not. These results confirm that GeNH2 is a predicted trivial insulator, but further research should be performed in straining the material in an attempt to induce a topological transition. We further confirm that GeI and SnI are topological insulators and have the potential to be utilized in the field of spintronics.”

Jordyn Hunter Paper

Name: Daniel Lesse

Undergraduate Institution: New Mexico Highlands University

Major: Chemistry

REU Advisor: Joshua Goldberger

Project Title:Hydrogen Absorbing Zintl-Phase SrGa₂: Synthesis and Semi-Hydrogenation Catalysis

Abstract: “A Zintl-phase can be defined as a substance comprised of 1st through 3rd group elements, along with post-transition metals. Zintl-phases are known to possess some interesting properties. The property we are interested in is the ability of electrondeficient Zintl-phases to absorb hydrogen. Another substance which has this ability is the Lindlar catalyst. This catalyst is used in the hydrogenation reduction of
phenylacetylene to make styrene, a popular monomer used to make a variety of plastics, rubbers, and expanded foam products. The Lindlar catalyst is rich in Pd, making it not only expensive, but also unsustainable. The ACS claims there is an undeniable risk to future supply. Therefore, it is in the best interests of humanity to develop new species of catalysts free of valuable transition metals. For the purposes of the following research, we focus on Zintl-phase hydrogenation catalysts, and explore the likelihood that they can replace conventional catalysts in the near future.”

 

Name: Chris Moore

Undergraduate Institution: University of Washington

Major: Comprehensive Physics and Astronomy

REU Advisor: Roberto Myers

Project Title: Towards optical detection of magnon Nernst in MnPS₃

Abstract: “Magnon spin Nernst has been spatially resolved through doubly modulated detection of the magneto-optical Kerr effect (MOKE) in the material MnPS3. A temperature gradient is created in the collinear antiferromagnet MnPS3 to induce magnon flows of opposite polarization in anti-parallel in-plane directions that are orthogonal to the gradient. This results in an induced spin current with a buildup of oppositely polarized magnon edge states. These edge states give rise to local surface magnetization which we probe for kerr rotation. This is the first documented optical detection of magnon spin nernst. Due to structural instabilities in the sample geometry a new sample stage was required to obtain higher confidence results. A new stage was designed and simulated in order to find the optimal material and geometry for a stable sample stage capable of inducing an appropriate temperature gradient through MnPS3.”

Chris Moore Paper

Name: Katherine Robinson

Undergraduate Institution: Wittenberg University

Major: Chemistry

REU Advisor: Roland Kawakami

 

Project Title: Optical characterization of spins and defects in thin films and heterostructures

Abstract: “This research focused on using optical techniques to characterize of thin film
materials, specifically Quantum Point Defect emitters and spin in heterostructures.
These are important in the field of spintronics, with possible application in other
fields such as quantum information. This research focused on three materials,
hexagonal Boron Nitride (hBN), Tungsten Diselenide (WSe2), and graphene. hBN is
used in heterostructures, where defects in the lattice are problematic [1]. However,
defects in hexagonal Boron Nitride in previous research has been found to be single
photon sources [2]. This research focused on learning more about defects in the hBN
lattice by making and characterizing defects in hBN. Tungsten Diselenide is a  semiconductor that is also used in heterostructures due to its interesting band structure that allows for spin/valley polarization and long spin/valley lifetimes [3]. Graphene, on
the other hand, has a short spin/valley lifetime but can transport spins and charge
carriers well [4]. These two materials were studied in heterostructures to learn more
about the spin movement and interaction between materials. Photoluminescence was taken on both hBN and heterostructures samples. Timeresolved Kerr rotation was used to investigate the spin/valley lifetimes of grapheneWSe2 heterostructures. In hBN, annealing and depositing an atomic layer of Chromium resulted in single photon source peak being found. In the graphene-WSe2 heterostructures, there was a decrease in excitation decay in the graphene overlap region versus the original Tungsten Diselenide flakes, suggesting the movement of spins and electrons from one material into the other.”

Katherine Robinson Paper