Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X60: Scattering and DiffractionFocus Live
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Sponsoring Units: GIMS Chair: Alex Frano |
Friday, March 19, 2021 8:00AM - 8:36AM Live |
X60.00001: Emerging capabilities for neutron scattering science at ORNL Invited Speaker: Ken Andersen N/A |
Friday, March 19, 2021 8:36AM - 9:12AM Live |
X60.00002: High-resolution RIXS with in-situ magnetic field as a probe of magon-spinon dichotomy in β-Li2IrO3 Invited Speaker: Alejandro Ruiz The family of tri-coordinated iridates have been identified as potential candidates supporting a Kitaev quantum spin liquid, in which spins fractionalize into emergent Majorana fermions and magnetic flux excitations. These quasiparticles acquire long-range topological entanglement and are ideal for fault-tolerant quantum computers. While the presence of additional interactions usually leads to conventional ordering, a dominant Kitaev exchange leads to QSL behavior after the magnetic order is suppressed by temperature or magnetic field, with signatures appearing in thermodynamic measurements and dynamical probes. |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X60.00003: Wide Angle Spherical Neutron Polarimetry at Oak Ridge National Laboratory Nicolas Silva, Tianhao Wang, Chenyang Jiang, Fankang Li, Lisa DeBeer-Schmitt, Masaaki Matsuda, Jillian Ruff, Roger Pynn Spherical Neutron Polarimetry (SNP) analyzes complex magnetic structures through distinguishing contributions from nuclear-magnetic interference and chiral structure in addition to nuclear magnetic scattering separation. This analysis is achieved through determining all components in the polarization transfer process. The SNP device consists of three units: incoming/outgoing neutron polarization, sample environment and a zero-field chamber. The incoming/outgoing neutron polarization regions use high- superconducting YBCO films and mu-metal to achieve full control of neutron polarization. The sample environment is an orange cryostat with a customized tail piece placed into the zero-field chamber. The device has been tested at the university of missouri research reactor (MURR) and at HYSPEC. While both experiments were fruitful, the testing at HYSPEC yielded more insight into improving the device and guiding the design. It is important to note that the testing at HYSPEC utilized HYSPEC as a triple-axis spectrometer. Upgrades to the device have been designed and are being fabricated while further testing has been designated for early 2021. |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X60.00004: Neutron Detection with a Work Function Reference Circuit Elaine Rhoades, Aaron Green, William Hunt A novel type of solid state particle detector has been designed and investigated. The core design is a bandgap reference circuit using gallium nitride (GaN) Schottky diodes, designed to output a voltage proportional to the Schottky barrier height. As a semiconductor, gallium nitride exhibits an electrical response to high-energy particle impingement through the creation of electron-hole pairs. It also exhibits an additional type of response to lattice vibrations induced in the crystal lattice by momentum transfer from the incident particle. Acoustic waves generated during this transfer create mechanical strain which induces an electric field via the piezoelectric effect, which subsequently modulates the effective barrier height of the Schottky diode. This talk presents experimental demonstration of a prototype circuit and its transient responses to alpha and neutron irradiation. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X60.00005: Progress towards a rapid-throughput MeV ultrafast electron diffraction system Mariana Fazio, Sandra G Biedron, Destry Monk, Manel Martínez-Ramón, Salvador Sosa Guitron, David Martin, Michael Papka, Marcus Babzien, Kevin A. Brown, Mark A Palmer, Jing Tao, Alan Hurd, Julian Chen, Rohit P Prasankumar, Christine Sweeney MeV ultrafast electron diffraction (MUED) is a powerful structural measurement technique for novel characterization of matter. It can determine fine structural details with ultrafast time resolving capability, enabling the study of structural transitions in a wide range of materials. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X60.00006: Effective Isolation of structures from external vibrations by means of discrete media
Hasson Tavossi, Department of Engineering Technology, Savannah State University, 3219 College St. Savannah, GA 31404. Hasson Tavossi Wave properties of the particulate media are explored to determine their vibration attenuation, by absorption and scattering of mechanical waves, as a function of material parameters, with the goal to effectively reduce vibration transmission into structures. Pressure wave, shear wave, and surface waves are considered. Wave speeds and attenuation in the discrete media depend on mechanical parameters of the media. Among these are; particulate size distribution, confining pressure, contact areas, and the compactness. Experimental results presented show that; for a fixed value of parameter; discrete media strongly attenuate vibrations in a frequency-band, and transmit vibrations outside that band. Different samples of particulates are subjected to mechanical vibrations, within a range of frequency and amplitude in direct contact with samples. Measurement of attenuation, transmitted intensity, and wave speed are presented with different media parameter. Experimental findings on attenuation as a function of frequency and intensity, and dispersion curve can provide discrete media properties for more effective means to attenuate of external vibrations transmitted into a structure. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X60.00007: Complex amplitude control in X-rays for maskless holography Kahraman Keskinbora, Abraham Levitan, Gisela Schütz, Riccardo Comin Phase-contrast imaging provides information about a sample‘s electronic structure, otherwise lost in absorption imaging. Many coherent diffractive X-ray imaging methods offer ways to probe electronic and magnetic ordering by tapping the phase component. Mainly, Fourier transform X-ray holography (FTH) emerged as a tool for single-shot imaging of ultrafast phenomena. FTH relies on the fabrication of a mask directly on the sample, limiting the experimental geometry, the suitable samples, and the region of interest. We describe a way to create a structured illumination to replace the holography mask. It is necessary to control both the amplitude and the wavefield phase using a diffractive optic leading to an immense increase in intensity on the sample, by efficient use of the coherent flux. We will discuss the implementation of the method via quantitative simulations. The technique enables imaging extended samples and broad physical phenomena of great importance, such as magnetism and metal-insulator transitions of quantum solids. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X60.00008: Improvement of accuracy and precision in refinement of crystal structure factors using zone-axis incidence and tilted CBED patters Bikas Aryal, Daisuke Morikawa, Kenji Tsuda, Masami Terauchi Crystal structure analysis method developed by Tsuda and Tanaka [1] has been applied for the refinement of isotropic atomic displacement parameters and structure factors of five low-order reflections of potassium tantalate (KTaO3). Structure factors determined from zone-axis (ZA) incidences and tilted convergent-beam electron diffraction (CBED) patterns are compared. Discussions about precisions and sensitivities of the ZA incidences and the tilted CBED patterns for refinements of the structure factors is made. CBED patterns taken at tilted incidences showed higher precisions for determination of the structure factors than ZA incidences. The present analysis reveals different tendencies of sensitivities of the ZA incidence patterns and the tilted CBED patterns to changes of the structure factors of reflections, suggesting to use both of them for higher sensitivity and precision in refinements of the structure factors. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X60.00009: Up- and Down-Conversion between Intra- and Intervalley Excitons in Waveguide Coupled Monolayer WSe2 Yueh-Chun Wu, Jun Yan, Sarath Samudrala, Andrew McClung, Amir Arbabi, Takashi Taniguchi, Kenji Watanabe We develop a waveguide coupled 1L tungsten diselenide (WSe2) device to probe its various exciton species. With TM and TE excitations, the optical fields can efficiently couple to the atomic layer's in-plane and out-of-plane dipole moments. Our work reveals several upconversion processes that bring out a coupling network linking spin-0 and spin-1 intra- and intervalley excitons, demonstrating that intervalley scattering and spin-flip are very common processes in the atomic layer. These experimental results deepen our understanding of tungsten diselenide exciton physics and illustrate that planar photonic devices are promising platforms for manipulating versatile exciton species in TMD semiconductors. |
Friday, March 19, 2021 10:36AM - 10:48AM Live |
X60.00010: In-situ TEM technique and Its Structural Manipulation in Metal Oxides Xuedong Bai The In-situ transmission electron microscopy (TEM) method is powerful in a way that it can directly correlate the atomic-scale structure with physical and chemical properties. In this presentation, we will report on the construction and applications of the in-situ TEM setup including mechanical, electrical and optical holders, which were built by scanning probe microscopy technique. So the manipulation and physical measurement have been realized inside TEM, where the atomic-scale imaging of electrically and/or mechanically driven structural evolution at atomic scale has been carried out by homemade in-situ TEM setup. |
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