Current Seminars and Colloquia - Fall 2021

Article Index

Fall 2021

Physics Department Colloquia and Seminars in 2021

PHYSICS Colloquium

September 16 2021, Thursday, 3:30 pm CST
Physical Sciences 110

iski erin 10122017Dr. Erin Iski  
Chemistry and Biochemistry
University of Tulsa


 

 

 

Visualizing Nanoscale Surface Chemistry: From Ultra-High Vacuum to Electrochemical Environments

Scanning tunneling microscopy (STM) is a specialized technique that can be used to examine and study nanoscale surface chemistry due to its extreme resolution. The requirement of pristine molecular resolution of certain systems necessitates the use of low temperature, ultra-high vacuum STM (LT-UHV STM) during the initial characterization of the surfaces. Importantly, it is also possible to study the assembly of molecules and atoms with liquid and electrochemical STM (EC-STM) in an attempt to bridge the temperature and pressure gap of ultra-high vacuum studies and to take measurements under more realistic conditions. The first investigation focuses on the EC-STM study of five simple amino acids (L-Valine, L-threonine, L-Isoleucine, L-Phenylalanine, and L-Tyrosine) as well as two modifications of a single amino acid (L-Isoleucine Ethyl Ester and N-Boc-L-Isoleucine), and the means by which these molecules interact with a Au(111) surface. Using EC-STM under relevant experimental conditions, the amino acids were shown to have a considerable interaction with the underlying surface. In some cases, the amino acids trapped diffusing adatoms to form Au islands and in other cases, they assisted in the formation of magic gold fingers. Importantly, these findings have also been observed under UHV conditions, but this is the first demonstration of the correlation in situ and was controlled via an external applied potential. Additional studies examining the role that surface temperature played in formation of the adatom islands will also be discussed. By analyzing the results gathered via EC-STM at ambient conditions, fundamental insight can be gained into not only the behavior of these amino acids with varied side chains and the underlying surface, but also into the relevance of LT-UHV STM data as it compares to data taken in more realistic scenarios. In the second project, EC-STM was used to study the deposition of Ag on Au(111), which in the presence of chloride, formed an ultra-stable layer that was stable in air and to temperatures as high as 1,000 K. Interestingly, depending on the exact potential used to form the Ag layer, a different type of thermal stability was observed. This atomically thin and ultra-stable layer which was also resistant to oxidation may find applications in a variety of fields and select anti-corrosion applications.

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PHYSICS Colloquium

September 23 2021, Thursday, 3:30 pm CST
Physical Sciences 110

 Narducci 9 2021Dr. Francesco (Frank) Narducci

 Naval Postgraduate School
Associate Editor: Physical Review A, Physical Review Letters
 

 

 

Towards a T3 atom interferometer

In this talk, I will discuss a novel atom interferometer being developed at the Naval Postgraduate School. I will begin the talk by reviewing the theory of light pulse atom interferometers, concentrating on how the phase of the interferometer scales with the time between the atom optic pulses, T.  I will discuss the connection between the Lagrangian and Hamiltonian formulations for the calculation of the phase.  Next, I will demonstrate that the T2 scaling is due to a symmetry in the problem and that when the symmetry is broken, a T3 scaling appears (and in our geometry, the phase becomes purely dependent on a T3 term with no T2 terms). I will then turn to a discussion of an experimental implementation involving interferometry on magnetic transitions. The experiment is quite challenging and, although the signature T3 signal has so far eluded us, has provided many interesting features and physics which I will discuss.

PHYSICS Seminar

September 23 2021, Friday, 11:30 am CST
Physical Sciences 110

 Narducci 9 2021Dr. Francesco (Frank) Narducci

 Naval Postgraduate School
Associate Editor: Physical Review A, Physical Review Letters
 

 

 

Successfully Publishing in Physical Review Letters/The Physical Review

In this talk, I will discuss the general editorial process that leads to the publication (or rejection) of a manuscript submitted to Physical Review Letters/The Physical Review.  In a humorous atmosphere, I’ll present the “dos and don’ts” associated with publishing in the APS journals, starting from the initial submission to our appeals process. Statistics associated with the journal will be presented (but kept to a minimum!)  Finally, I’ll present some of our recent initiatives. Humorous stories will be injected throughout the talk.

PHYSICS Colloquium

September 30 2021, Thursday, 3:30 pm CST
Physical Sciences 110

 TomanekDr. David Tománek

 Michigan State University

 

 

 

 

Saving Humankind from Thirst

Whereas water itself is bountiful on Earth, much of it requires treatment to make it suitable for human consumption. Lack of potable water is currently the leading cause of death, ahead of any disease. Recent progress in fabricating nanostructured carbon allotropes may bring a long-awaited paradigm shift in designing membranes that would make efficient desalination of salt water using reverse osmosis and filtration of contaminated water possible. A previously unexplored membrane design [1] based on a unique layered assembly of carbon nanostructures including graphite oxide (GO), buckypaper consisting of carbon nanotubes, and a strong carbon fabric should provide high mechanical strength and thermal stability, resilience to harsh chemical cleaning agents and electrical conductivity, thus addressing major shortcomings of commercial reverse osmosis membranes. Microscopic insight into the critical permeation of water molecules in-between GO layers and across in-layer vacancy defects in graphitic carbon can be obtained using ab initio density functional theory calculations. Results of these computational studies elucidate the reason for selective rejection of solvated Na+ ions in an optimized layered all-carbon membrane.

[1] David Tománek and Andrii Kyrylchuk, Designing an All-Carbon Membrane for Water Desalination, Phys. Rev. Applied 12, 024054 (2019).

 

PHYSICS Colloquium

October 28 2021, Thursday, 3:30 pm CST
Via Zoom (contact Physics Department for link)

 

Dr. Phillip Ryan

Argonne National Laboratory

 

X-ray scattering and Electrical Measurements of Uniaxially Strained Single Crystals: Unconventional Superconductors and Single Phase Multiferroicity

In this presentation I will layout a brief overview of my research at the Advanced Photon Source (APS) with some recent results and describing a vision of what I plan for in the post source upgrade (APS-U) after 2023. The Magnetic Materials Group primarily serves the condensed matter community providing resonant hard x-ray magnetic scattering for single crystal systems, with a particular interest in epitaxial thin films (1). To drive our leading-edge scientific abilities, we continuously develop metrological tools which are made available to the community at large. Here, I will introduce recent developments to drive CMP scientific endeavors forward including low temperature uniaxial strain in a multimodal setup, and dynamic in-situ measurement configuration. Presenting recent results on single crystal unconventional superconducting pnictide systems BaFe2As2 parent compound we demonstrate in-situ uniaxial strain capability with commensurate electrical measurements (2-4).

In addition, I will present results from the intriguing, rare earth–titanate, EuTiO3. This material is an excellent platform to explore the interplay between spin, charge, and symmetry within a single system (5-7) and to expand the sample environment control capabilities that now serve a broader range of scientific interests. We try to untangle the magnetoelectric behavior in this single-phase system and in the process demonstrate a ‘giant’ ME cross-field control capability in the rare earth perovskite (5). In bulk form it is both antiferromagnetic and paraelectric. Both anti- and ferro- magnetic interactions are present between different nearest europium neighbors allowing for the notion of magnetic quantum criticality through a combination of doping or strain (8). Fortuitously, like SrTiO3, this system is also considered potentially quantum paraelectric or ‘incipient’ ferroelectric, this conjures the notion of bi-criticality or possibly the emergence of a coupled multiferroic quantum critical point (8).

  1. https://www.aps.anl.gov/Sector-6/6-ID-B-C/Publications
  2. Suppression of superconductivity by anisotropic strain near a nematic quantum critical point, P. Malinowski, et. al., Nature Physics, 1-5, (2020)
  3. The transport–structural correspondence across the nematic phase transition probed by elasto X-ray diffraction, JJ Sanchez, P Malinowski, J Mutch, J Liu, JW Kim, PJ Ryan, JH Chu, Nature Materials, 1-6 (2021)
  4. Strongly anisotropic antiferromagnetic coupling in EuFe2As2revealed by stress detwinning, Joshua J. Sanchez, Gilberto Fabbris, Yongseong Choi, Yue Shi, Paul Malinowski, Shashi Pandey, Jian Liu, I. I. Mazin, Jong-Woo Kim, Philip Ryan, and Jiun-Haw Chu, Phys. Rev. B 104, 104413 – Published 10 September 2021
  5. Reversible Control of Magnetic Interactions by Electric Field in a Single, P.J. Ryan et al, Nat. Commun. 4:1334, (2013)
  6.  Emergent Superstructural Dynamic Order due to Competing Antiferroelectric and Antiferrodistortive Instabilities in Bulk EuTiO3, J-W Kim, et al, Phys, Rev. Lett. 110, 027201 (2013).
  7. Multiferroic behavior in EuTiO3 films constrained by symmetry, P.J. Ryan, et. al., Phys. Rev. B 101, 180409 (2020)
  8. Multiferroic quantum criticality, Narayan, Andrés Cano, Alexander V. Balatsky, Nicola A. Spaldin, Nat. Mat. VOL 18 | MARCH 2019 | 223

 

PHYSICS Colloquium

November 4 2021, Thursday, 3:30 pm CST
Physical Sciences 110
marino crop

 Dr. Alberto Marino

 University of Oklahoma

 

 

 

 

Quantum-Enhanced Sensing with Light

There is a significant effort to take advantage of quantum resources, such as entanglement and superposition, to enhance measurements and devices in a way not possible with classical resources. This has led to the development of the emerging area of quantum technologies. Quantum optics will play a significant role in this so called “Second Quantum Revolution” due to the precise control and characterization that can be achieved with light. In this talk I will give an overview on the use of quantum states of light to enhance optical based sensors beyond the classical limit given by the shot noise. I will focus on our work on the interface between entangled twin beams of light and plasmonic sensors and show that a quantum-based sensitivity enhancement can be obtained. I will then describe the fundamental limits to the quantum enhancement that can be achieved. Finally, I will present our most recent work on the implementation of a parallel quantum-enhanced sensing approach.

 

PHYSICS Seminar: OKPVRI Plenary Symposium (hosted by Dr. Ian Sellers at OU)

November 16 2021, Tuesday, 10:00 am CST
Online via Zoom, Registration at: https://forms.gle/brETcQzVgtoJHgya7

Dr. Louise Hirst

University of Cambridge

 

Ultra-thin photovoltaics for space power applications

Space base services, such as real time imaging of the Earth’s surface and global communication networks are critical to many aspects of our modern lives. These services rely on satellite systems with payloads powered by solar cells. High efficiency III-V multijunction photovoltaic devices are standard for space power applications, in part due to their high performance and corresponding high specific power (W/kg), as well as their relative radiation tolerance, although increasingly other material systems are being considered for certain use cases. In this talk, the requirements for space power systems will be discussed along with key challenges driving innovation in the field. Ultra-thin geometries (active device thickness ~100 nm), offer many advantages for future satellite systems including flexible form factors for conformal system integration; reduced cost, materials usage and launch mass; and intrinsic radiation tolerance enabling new mission profiles in highly damaging environments. The challenges associated with moving to ultra-thin geometries will be discussed including the development of novel nanophotonic light management systems to obtain full solar absorption in ultra-thin films, along with the practical fabrication approaches for such systems.

PHYSICS Colloquium

November 11 2021, Thursday, 3:30 pm CST
Physical Sciences 110

 ManolissDr. Manolis Kargiantoulakis

 Fermilab
 
 

 

 

 

The Muon Anomalous Magnetic Moment: First results from the Fermilab Muon g-2 Experiment 

The Muon g − 2 Experiment at Fermilab has measured the anomalous magnetic moment of the muon to 460 parts-per-billion, based on data collected during the first physics run in 2018. The experiment determines the anomalous precession frequency of the muon spin inside the highly uniform and precisely measured magnetic field of our storage ring. Our result is consistent with the BNL measurement of the same quantity from nearly two decades ago. The experimental combination increases the tension with the Standard Model prediction, enhancing the significance of the discrepancy to 4.2σ. In this colloquium we will give an overview of the experimental measurement and discuss the status of the discrepancy, and why it could be very important for particle physics.

PHYSICS Colloquium

November 18 2021, Thursday, 3:30 pm CST
Online Via Zoom

 WuDr. Weida Wu

 Rutgers University
 
 

 

 

 

Berry Phase and Related Hall Effects

The Berry phase is the geometric phase of wavefunction in parameter space1. It underscores many interesting topological phenomena, especially various quantized or anomalous Hall effects1,2.  The quest for quantum Hall effect (QHE) without external magnetic field leads to the exciting development of quantum spin Hall effect (QSHE)3, the emergence of topological classification of band insulators4, and eventually the realization of quantum anomalous Hall effect (QAHE)5. In parallel to the fascinating evolution of Berry phase phenomena in the momentum space, there is also a real space counterpart, the topological Hall effect (THE) which is associated with non-coplanar spin textures with scalar spin chirality. As such, the THE provides a powerful probe of the ground state and low-energy excitations of magnetic metals. I will present our recent research progress on the QAHE and the THE in magnetic thin films using magnetic imaging technique with in-situ transport6–8.

References

  1. Xiao, D., Chang, M. C. & Niu, Q. Berry phase effects on electronic properties. Rev. Mod. Phys. 82, 1959–2007 (2010).
  2. Nagaosa, N., Sinova, J., Onoda, S., MacDonald, A. H. & Ong, N. P. Anomalous Hall effect. Rev. Mod. Phys. 82, 1539–1592 (2010).
  3. Kane, C. L. & Mele, E. J. Z2 topological order and the quantum spin Hall effect. Phys. Rev. Lett. 95, 146802 (2005).
  4. Fu, L., Kane, C. L. & Mele, E. J. Topological Insulators in Three Dimensions. Phys. Rev. Lett. 98, 106803 (2007).
  5. Chang, C.-Z. et al. Experimental Observation of the Quantum Anomalous Hall Effect in a Magnetic Topological Insulator. Science 340, 167–170 (2013).
  6. Wang, W. et al. Direct evidence of ferromagnetism in a quantum anomalous Hall system. Nat. Phys. 14, 791–795 (2018).
  7. Wang, W. et al. Spin chirality fluctuation in two-dimensional ferromagnets with perpendicular magnetic anisotropy. Nat. Mater. 18, 1054–1059 (2019).
  8. Wang, W. et al. Chiral-Bubble-Induced Topological Hall Effect in Ferromagnetic Topological Insulator Heterostructures. Nano Lett. 21, 1108–1114 (2021).