Seminars and Colloquia, July through December, 2014


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Seminars and Colloquia, Typical Week:


Frontiers of Physics:

Date:Monday
Time:3:30 PM
Place:PS 355
Inquiries: pos@okstate.edu

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Date:Thursday
Time:1:30-3:00 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Inquiries: joseph.haley@okstate.edu or kao@nhn.ou.edu

Physics Colloquium:

Date:Thursday
Time:3:30-4:30 PM
Place:PS 101
Inquiries: s.nandi@okstate.edu or perk@okstate.edu

Journal Club on Statistical Mechanics and Condensed Matter Physics, and Optics (Informal):

Date:Friday (bi)weekly
Time:2:00 PM
Place:PS 147
Inquiries: perk@okstate.edu or girish.agarwal@okstate.edu

Oklahoma State Physics Department

Seminars and Colloquia, July 1-4, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, July 7-11, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, July 14-18, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, July 21-25, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, July 28-August 1, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, August 4-8, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, August 11-15, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, August 18-22, 2014


First week of classes

No colloquium scheduled.


Oklahoma State Physics Department

Seminars and Colloquia, August 25-29, 2014


Second week of classes.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Liangliang (Paul) Huang
School of Chemical, Biological and Materials Engineering
University of Oklahoma
Date:Friday, August 29, 2014
Time:2:30 PM
Place:PS 148 (and room 103 Nielsen Hall, OU)
Title:Multi-Scale Modeling of Chemical Reaction: Examples in Chemical Engineering

Abstract:

Chemical reactions are often carried out on catalytic surfaces or in macro- and nanoporous materials, which the confinement effect can change the reaction pathway or enhance reaction rates and equilibrium yields. From the theoretical point of view, the study of confinement effect is a process correlated with adsorption, diffusion and chemical reactions, and thus requires multi-scale computational efforts.

In this seminar, I will discuss three computational calculation examples of chemical reactions: the dissociation of gas-phase hydrogen sulfide and ammonia by using graphene oxide (GO) and CuBTC metal-organic framework (MOF), and the behavior of water on or near the titanium dioxide (TiO2) surfaces. Results from ab initio density functional theory (DFT), classical molecular dynamics (MD), Grand Canonical Monte Carlo (GCMC) calculations and reactive force field (ReaxFF) method will be discussed. Corresponding experimental results will also be provided for each example.

Other related projects and future research directions on chemical reaction and interface engineering will be briefly discussed, including the surface functionalization of graphene oxide and its application in biomedical engineering, the study of nanofriction by a combination of atomic molecular dynamics simulations and atomic force microscope (AFM) experiments.

Keywords: reactive adsorption, chemical reaction, graphene oxide, metal-organic framework, titanium dioxide, reactive force field, surface functionalization, nanofriction, interface engineering, catalysis


Oklahoma State Physics Department

Seminars and Colloquia, September 1-5, 2014


Labor Day Holiday Monday September 1.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Bin Wang
School of Chemical, Biological and Materials Engineering
University of Oklahoma
Date:Friday, September 5, 2014
Time:2:30 PM
Place:PS 148 (and room 103 Nielsen Hall, OU)
Title:Tunable Electronic and Optical Properties of Two-Dimensional Materials and Transition Metal Oxides

Abstract:

Tunable electronic and optical properties of nanomaterials are valuable for their applications in electronic and optical devices, molecular sensors, and catalysis. In this talk  I will discuss several case studies of two-dimensional (2D) materials and transition metal oxides, through which I would like to demonstrate how experiments and computational simulations could be combined to address various issues. In the first example, the structure, growth dynamics, and template effect of monolayer graphene and h-BN on metal surfaces will be discussed. Second, I will focus on 2D transition metal dichalcogenides such as MoS2. Particularly I will talk about the large exciton binding energy and tunable band structure and optical spectrum of MoS2 under tensile strain. In the third example, I will highlight the strong interplay between different degrees of freedom in vanadium dioxide, a phase change material, and discuss how to tailor the phase transition temperature by creating hybrid structures and electron injection.


Oklahoma State Physics Department

Seminars and Colloquia, September 8-12, 2014


Geology Seminar:

Speaker:Dr. Robert B. Finkelman
Department of Geosciences
University of Texas at Dallas
Date:Friday, September 12, 2014
Time:12:30 PM
Place:NRC 108
Title:Medical Geology: How the Natural Environment Gets Away with Murder (and Saves Lives, too)

OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Jivtesh Garg
School of Aerospace and Mechanical Engineering
University of Oklahoma
Date:Friday, September 12, 2014
Time:2:30 PM
Place:PS 148 (and room 103 Nielsen Hall, OU)
Title:Higher Efficiency Thermoelectrics through Ab-initio and Monte Carlo Simulations of Phonon
and Electron Transport in Nanostructured Semiconductor Materials

Abstract:

Thermoelectrics convert temperature gradient into useful electric power. The energy conversion efficiency is directly proportional to electrical conductivity and square of Seebeck coefficient and inversely proportional to thermal conductivity. Different approaches to enhance thermoelectric efficiency focus on increasing Seebeck coefficient and electrical conductivity and decreasing thermal conductivity. In semiconductor materials heat is partly conducted by phonons and thermal conductivity can be engineered independent of the electrical conductivity. This talk will focus on the first-principles methods to predict phononic thermal transport in semiconductors based on deriving the second-order and third-order interatomic force constants from density-functional theory. Superlattice structures optimize different phonon scattering mechanisms and provide avenues to achieve ultra-low thermal conductivity beneficial for thermoelectrics. Finally their low thermal conductivity can be combined with an enhancement of Seebeck coefficient through the use of heterostructures to yield high thermoelectric efficiency. To this end Monte-Carlo simulations of electron transport in single-barrier heterostructures will be discussed.


Oklahoma State Physics Department

Seminars and Colloquia, September 15-19, 2014


Physics Colloquium:

Speaker:Dr. John Wisniewski
Homer L. Dodge Department of Physics & Astronomy
University of Oklahoma
Date:Thursday, September 18, 2014
Time:3:30 PM
Place:PS 110
Title:Diagnosing the SEEDS of Planet Formation

Abstract:

Circumstellar disks provide a useful astrophysical diagnostic of the formation and early evolution of exoplanets.  It is commonly believed that young protoplanetary disks serve as the birthplace of planets, while older debris disks can provide insight into the architecture of exoplanetary systems.  In this talk, I will discuss how one can use high contrast imaging techniques to spatially resolve nearby circumstellar disk systems, and how this imagery can be used to search for evidence of recently formed planetary bodies.  I will focus on results from the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) project.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Lucas K. Wagner
Department of Physics
University of Illinois at Urbana-Champaign
Date:Friday, September 19, 2014
Time:2:30 PM
Place:PS 148 (and room 103 Nielsen Hall, OU)
Title:Explicitly Simulating Electron Correlations in Realistic Models of Materials

Abstract:

Traditional electronic materials operate in the weakly interacting regime; it is a good approximation to assume that the electrons do not interact with one another in describing the behavior of the material. Part of the next generation of materials requires us to discard this approximation to enable new emergent behaviors such as unconventional superconductivity, colossal magnetoresistance, and ultrafast optical switching. However, full treatment of the many-body quantum problem is very challenging, with general purpose numerical algorithms scaling exponentially with system size.

I will discuss new applications of approximate quantum Monte Carlo techniques to ab-initio models of strongly correlated systems. Starting from fundamental constants and the positions of the nuclei, we calculate the collective motions of electrons and derive effective low energy models. We have found that the approximations can be controlled well enough to accurately predict experimental results and gain physical insight on challenging systems such as vanadium dioxide, graphene, and the cuprate parent materials of high temperature superconductors.


Oklahoma State Physics Department

Seminars and Colloquia, September 22-26, 2014


No colloquium scheduled, because of conflict with OSU football program.


Chemistry Seminar:

Speaker:Dr. Catherine J. Murphy
Peter C. and Gretchen Miller Markunus Professor of Chemistry
Department of Chemistry
University of Illinois at Urbana-Champaign
Date:Thursday, September 25, 2014
Time:3:30 PM
Place:PS 103
Title:Molecular Engineering of Gold Nanorod Surfaces

Abstract:

Gold nanorods have tunable plasmon resonances throughout the visible and near-infrared portions of the spectrum. These optical properties enable both fascinating science and fascinating applications in optics, biosensing, imaging agents, and photothermal therapeutics. In this talk I will discuss how we make and measure the molecules on the surface of the nanorods, and how molecular display impacts physicochemical properties of these nanomaterials “downstream.”

Note: Instead of refreshments at 3:00 pm, we would like to invite you to join us on the south lawn of PS1 for a tailgate gathering immediately following the seminar.


Oklahoma State Physics Department

Seminars and Colloquia, September 29-October 3, 2014


Special Seminar

Sponsored by the Department of Microbiology and Molecular Genetics and the Department of Biochemistry and Molecular Biology:

Speaker:Dr. Aihua Xie
Department of Physics
Oklahoma State University
Date:Monday, September 28, 2014
Time:3:30 PM
Place:348B Nobel Research Center
Title:OSU Advanced FT-IR User Facility:
Open New Opportunities for Multi-disciplinary Research and Education

Abstract:

The OSU Advanced FT-IR User Facility, jointly funded by NSF MRI and OSU, will soon open its door to researchers. Unlike X-ray crystallography and NMR spectroscopies, the research capabilities of infrared structural biology and infrared imaging are not so familiar to many prospective users. In this talk, I will give an overview of this highly integrated state-of-the-art FT-IR system, the rapid growing possibilities for addressing biological questions using infrared approaches, and will discuss specific examples of how different FT-IR technologies are applied to solve biological problems. In addition, I will address different platforms for project exploration and user training.


Physics Colloquium:

Speaker:Dr. Zhe-Yu Jeff Ou
Department of Physics
Indiana University–Purdue University Indianapolis (IUPUI)
Date:Thursday, October 2, 2014
Time:3:30 PM
Place:PS 110
Title:Interferometers with Non-traditional Beam Splitters

Abstract:

We will discuss a new type of interferometers that employ nonlinear devices as beam splitters. A specific scheme with parametric amplifiers, the so called SU(1,1) interferometer, is implemented and is compared with a traditional linear interferometer. A new paradigm for quantum interferometry is found that is different from the noise reduction mechanism in squeezed state interferometry. Furthermore, the nonlinear process allows the coupling of different types of waves and leads to hybrid interferometry involving different waves. A specific atom-light hybrid interferometer will be discussed.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Louise C. Hirst
US Naval Research Laboratory, Washington, DC
Date:Friday, October 3, 2014
Time:2:30 PM
Place:Room 103, Nielsen Hall, OU
Title:How to Build a Hot-Carrier Solar Cell: Materials Development and Device Design

Note: Unfortunately, this and the later ones in this series could not be received at OSU due to technical problems.

Abstract:

In traditional single-junction solar cells > 50 % of incident solar radiation is lost through the dissipation of heat energy to the ambient or the transmission of low energy photons. The hot-carrier solar cell (HCSC) targets these intrinsic loss mechanisms allowing for high efficiency photovoltaic conversion. The HCSC is a device in which the photo-excited carrier population does not form a thermal equilibrium with the surrounding lattice and thus, heat energy is prevented from dissipating to the ambient. Non-equilibrium hot-carriers are then selectively extracted with energy above the bandgap energy of the absorber. In this way, the HCSC is a fundamentally more efficient heat engine than incumbent single-junction technologies.

HCSCs have two distinctive design requirements which represent development challenges: absorbers with restricted electron-phonon interaction and contacts for energy selective carrier extraction. In recent months there have been significant advances in HCSC development, with proof-of-concept demonstrations of primitive functionality.

In this talk, HCSC physics concepts will be explained and a practical guide to the development of a real world device will be presented. Recent progress in this field will be discussed along with some of the experimental and simulation techniques which have enabled this progress. Finally, possible solutions to some key remaining challenges will be considered and the crucial next steps that are required to transition this device from laboratory curiosity to practical energy converter will be highlighted.


Computational Materials Seminar:

Speaker:Dr. Mario F. Borunda
Department of Physics
Oklahoma State University
Date:Friday, October 3, 2014
Time:4:00 PM
Place:Engineering North 516
Title:Searching for the Needles in a Molecular Haystack:
Computational Assessment of Organic Photovoltaic Candidate Compounds

Abstract:

Organic photovoltaic (OPV) cells are emerging as a possible renewable alternative to petroleum based resources and are needed to meet our growing demand for energy. Solar cells made of thin photovoltaic materials such as crystalline silicon can harvest energy with 25% efficiency. Yet, high production costs have limited their widespread use. Although not as efficient as silicon based cells, OPV cells have as an advantage that manufacturing cost is potentially lower. The Harvard Clean Energy Project, using a cheminformatic approach of pattern recognition and machine learning strategies, has ranked a molecular library of 2.6 million candidate compounds based on their performance as possible OPV materials. Here, we present a ranking of the top 1000 molecules for use as photovoltaic materials based on their optical absorption properties obtained via time-dependent density functional theory. This computational search has revealed the molecular motifs shared by the set of most promising molecules.


Oklahoma State Physics Department

Seminars and Colloquia, October 6-10, 2014


Physics Colloquium:

Speaker:Dr. Gaurav Bahl
Department of Mechanical Science and Engineering
University of Illinois at Urbana-Champaign
http://bahl.mechse.illinois.edu
Date:Thursday, October 9, 2014
Time:3:30 PM
Place:PS 110
Title:Brillouin Optomechanical Systems and Optomechanical Non-reciprocity

Abstract:

In recent years, resonant photonic microdevices have emerged that use extremely subtle optical forces such as radiation pressure, optical electrostriction, and gradient force, to couple light to radio- and microwave-frequency mechanical vibrations. These “Photonic MEMS” or “Optomechanical Oscillators” are promising tools for building compact frequency references, for fundamental experiments in nonlinear optics and achieving quantum-mechanical ground state, and also for extreme-sensitivity sensor applications (acceleration, displacement, mass, force, and gravity waves).

Our team’s work has focused on a different aspect of optomechanics—Using optical electrostriction in conjunction with Brillouin scattering to coupling traveling optical waves to traveling acoustic waves in ultra-high-Q resonators. In my talk I will discuss these mechanisms and some of the applications we have explored in parametric self-excitation and cooling. We have also developed the first microfluidic optomechanical device capable of chemical/biological/physical investigations on arbitrary analytes.

More recently, we have begun investigating the non-reciprocity behaviors that are intrinsic to these Brillouin optomechanical devices. I will describe our group’s experiment showcasing the first optomechanical system in which a non-reciprocal induced transparency has been observed.

Biographical Sketch:

Dr. Gaurav Bahl is an Assistant Professor of Mechanical Science and Engineering at the University of Illinois at Urbana-Champaign (UIUC), and an Affiliate Faculty in the Department of Electrical and Computer Engineering. Dr. Bahl received his PhD and MS degrees in EE from Stanford in 2010 and 2008, and BEng degree in ECE from McMaster University in 2005. He has authored the first experimental papers on parametric excitation and cooling through “Brillouin Optomechanics ”. His work on Brillouin systems (cooling and microfluidics) has been featured as a “(top-30) significant development in optics ” for two years in a row in the Optics in 2012 and Optics in 2013 special issues of the OSAs monthly Optics & Photonics News magazine. Additional commentary by editors and prominent researchers on the significance of his Brillouin optomechanics work has appeared in Nature Physics, Nature Photonics, and many technical news websites.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.


Oklahoma State Physics Department

Seminars and Colloquia, October 13-17, 2014


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Speaker:Dr. Flera Rizatdinova
Department of Physics
Oklahoma State University
Date:Thursday, October 16, 2014
Time:1:30 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Title:Top Quark Cross Section Measurements with the ATLAS Detector

Abstract:

I will discuss the recent public measurements of the inclusive, fiducial and differential ttbar cross section measurements made by the ATLAS Collaboration. Thanks to the high production cross section of top quark pairs at the LHC, the top quark physics entered the phase of the precise measurements. Results can be used to constrain the theoretical approaches to NNLO+NNLL calculations, used for the tuning of the Monte Carlo generators, and to constrain the Initial and Final state radiation and parton distribution functions.


No colloquium this week.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Rui Q. Yang
School of Electrical and Computer Engineerin
University of Oklahoma
Date:Friday, October 17, 2014
Time:2:30 PM
Place:Room 103, Nielsen Hall, OU
Title:20 Years of Interband Cascade Lasers and Related Devices

Abstract:

Interband cascade (IC) lasers are quantum-engineered mid-infrared (IR) lasers that combine the advantages of conventional interband diode lasers and quantum cascade (QC) lasers. It has been 20 years since the proposal of the IC laser concept in a poster presentation at the 7th International Conference on Superlattices, Microstructures and Microdevices, held in August of 1994. This talk will discuss, from a retrospective view, how IC lasers have been developed from an initial concept to practical devices, and how the concept has been expanded to other related optoelectronic devices such as IC IR photodetectors (ICIPs) and photovoltaic cells. Personal opinions and comments on some subjects will be given along with the discussion.


Oklahoma State Physics Department

Seminars and Colloquia, October 20-24, 2014


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Speaker:Dr. Pham Q. Hung
Department of Physics
University of Virginia
Date:Thursday, October 23, 2014
Time:1:30 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Title:Various Implications of the EW νR Model:
The dual nature of the 126-GeV SM-like Higgs boson; the neutrino and charged lepton mass matrices

Abstract:

In the EW νR model, Majorana masses for the right-handed neutrinos (which are now non-sterile) come from the vacuum expectation value of a Higgs triplet of SU(2) and are proportional to the electroweak scale 246 GeV. It implies that one can search for right-handed neutrinos at colliders such as the LHC and directly probe the seesaw mechanism. The model involves a Higgs sector larger than the SM doublet. It is shown that it can accommodate the 126-GeV SM-like Higgs boson with a caveat that this boson might be an impostor. Other scalars of the model turn out to have an interesting implication concerning lepton mass matrices.


Physics Colloquium:

Speaker:Dr. Pham Q. Hung
Department of Physics
University of Virginia
Date:Thursday, October 23, 2014
Time:3:30 PM
Place:PS 110
Title:Unraveling the Mysteries of the Neutrinos at the Large Hadron Collider

Abstract:

Why neutrinos are not massless and are so much lighter than the lightest of known charged elementary particles—in this case the electron—is a mystery that still eludes us. The tininess of neutrino masses might have its origin at energy scales probed by the Large Hadron Collider (LHC). In this talk, we will explore the possibility that the LHC might help us to unravel this mystery through the search for particles and phenomena which might have a direct impact on the origin of neutrino masses.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.


Students’ Fall Break Friday, October 24.


Oklahoma State Physics Department

Seminars and Colloquia, October 27-31, 2014


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Speaker:Dr. Kimball A. Milton
Homer L. Dodge Department of Physics & Astronomy
University of Oklahoma
Date:Thursday, October 30, 2014
Time:1:30 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Title:Gravitational Interaction of Quantum Vacuum Energy:
How does Casimir energy fall?

Abstract:

Several years ago we demonstrated that the Casimir energy for perfectly reflecting and imperfectly reflecting parallel plates gravitated normally, that is, obeyed the equivalence principle. At that time the divergences in the theory were treated only formally, without proper regularization, and the coupling to gravity was limited to the canonical energy-momentum-stress tensor. Here we strengthen the result by removing both of those limitations. We consider, as a toy model, massless scalar fields interacting with semitransparent (δ-function) potentials defining parallel plates, which become Dirichlet plates for strong coupling. We insert space and time point-split regulation parameters, and obtain well-defined contributions to the self-energy of each plate, and the interaction energy between the plates. (This self-energy does not vanish even in the conformally-coupled, strong-coupled limit.) We also compute the local energy density, which requires regularization near the plates. In general, the energy density includes a surface energy that resides precisely on the boundaries. This energy is also regulated. The gravitational interaction of this well-defined system is then investigated, and it is verified that the equivalence principle is satisfied.


Physics Colloquium:

Speaker:Dr. Sergey Sholom
Department of Physics
Oklahoma State University
Date:Thursday, October 30, 2014
Time:3:30 PM
Place:PS 110
Title:Emergency OSL, TL and EPR Dosimetry with Different Materials

Abstract:

There is an increasing risk for millions of people to be exposed to unknown radiation doses due to a radiological facilities accident (like the Fukushima Daiichi nuclear disaster in Japan) or a possible nuclear terrorist attack. In case of such event, radiation doses should be estimated quickly to triage victims according to the level of obtained doses. The main goal of this research was to develop new dosimetry techniques using different materials for post factum reconstruction of emergency doses.

Several materials were studied as possible emergency dosimeters. The materials included human teeth and nails as well as items that people may commonly have close to their bodies. These include paper currency (banknotes) and coins of different denomination and from different countries; plastic cards of different types (credit and debit cards, driver’s license cards, membership cards, etc.), business cards, parts and details of clothing and shoes as well as samples of different fabrics. Also studied were different building materials. The dosimetry methods included: Optically Stimulated Luminescence (OSL), Thermoluminescence (TL) and Electron Paramagnetic Resonance (EPR) techniques.

The main dosimetric properties were tested, including characterization of OSL/TL/EPR signals of materials before and after exposure, dose response curves, variability between different samples, and stability of the signals after exposure. Values of minimum measurable doses were determined and were below 2 Gy for most tested samples if measurements were conducted within one week of exposure and the samples were properly stored.>/P>

It was concluded that, under certain constrained circumstances, most of tested materials could be used as emergency OSL/TL/EPR dosimeters in triage applications.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.


Oklahoma State Physics Department

Seminars and Colloquia, November 3-7, 2014


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Postponed because of DOE site visits at OSU and OU.


Joint Physics/Chemistry/Biochemistry Colloquium/Seminar:

Speaker:Dr. Mikio Kataoka
Professor and Executive Director/Vice President
Nara Institute of Science and Technology (NAIST), Nara, Japan
Date:Thursday, November 6, 2014
Time:3:00 PM (Note time change!)
Place:PS 103
Title:Structure and Photoreaction of Photoactive Yellow Protein

Abstract:

Light energy conversion is essential in biology. We study the molecular mechanism of this process using photoactive yellow protein (PYP). Absorption of a photon triggers a complex series of structural events in PYP. Changes in the hydrogen bonding network at the photochemically active site of PYP result in proton transfer and large conformational changes. Using large PYP protein crystals prepared in our lab, we performed neutron crystallography and picosecond time-resolved X-ray crystallography. We determined the positions of 819 out of the 942 hydrogen atoms in PYP. In addition, we found an unusual low barrier hydrogen bond at the photoactive site. Our structures of short-lived photointermediate states revealed locally distorted structures. An atomic resolution movie of these structural changes will be presented at the seminar.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 105 at 4:00 PM. All students are welcome! Refreshments will be served.


Department of Chemistry Seminar:

Speaker:Dr. Teri W. Odom
Department of Chemistry, Northwestern University, Evanston, IL
Date:Thursday, November 6, 2014
Time:4:30 PM
Place:PS 103
Title:Gold Nanostar Probes for Imaging and Therapeutics

Abstract:

Nanotechnology offers new strategies for minimally invasive and localized approaches to diagnose and treat diseases. Recently, nanoparticles have been explored in a range of applications, including as drug delivery vehicles, imaging probes, and therapeutic agents. Although increased therapeutic efficacy has been realized, direct visualization of how engineered nanoparticles interact with specific organelles or cellular components has seen limited attention. Such interactions will have implications for fundamentals in cancer biology as well as in the design of translational therapeutic agents. This talk will describe how drug-loaded gold nanostars can behave as multi-spectral optical probes for interrogating how therapeutic nanoconstructs affect cancer cells at the nanoscale. We will focus on model cancer cell systems that can be used to visualize how gold nanostar nanoconstructs target cells, rotate on the plasma membrane, are endocytosed, and are trafficked intracellularly. We will also discuss mechanisms of cell death associated with these unique therapeutic nanoconstructs.

Note: Refreshments will be served at 4:00 pm in Physical Science 105.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Salvador Barraza-Lopez
Department of Physics
University of Arkansas
Date:Friday, November 7, 2014
Time:2:30 PM
Place:Room 103, Nielsen Hall, OU
Title:Adventures in Materials Flatland: Geometrical characterization of two dimensional materials
straight out from atoms, and the most stable phase of two-dimensional tin

Abstract:

Two-dimensional materials are atom-tin elastic nets that are mostly surface. The properties of this new class of materials depend on a fundamental way on their shape, which serves as a fundamental handle to tune their physical and chemical properties. What is the shape of a collection of atoms? The common answer consists on fitting the actual atomic mesh onto an effective continuum, and using differential geometry to determine four invariant quantities from the eigenvalues of the metric and curvature tensors: These four invariants determine the local geometry at any point of this smooth surface. This presents a conundrum: If shape is so fundamental for 2D materials, why is it relegated to fitting effective continuum media?

There exists a fundamental way to tell the shape of two-dimensional materials which emphasizes the fact that they are atomistic nets; everybody has been exposed to this framework within state-of-the-art animated movies: The field of discrete differential geometry (DDG) [1] has evolved parallel to the field of two-dimensional materials without any cross-fertilization so far. My team has been exploring possible applications of DDG into 2D materials [2-4]. Besides providing a description of shape that rests on atomic positions, not requiring continuum-based interpretations of an atomistic mesh, the discrete geometry can lead to a description of Chemistry under a deformed two-dimensional material. This description does not exist today, because a continuum medium is atom-less and hence inert for the purposes of Chemistry, thus highlighting the fact that the way one thinks or perceives shape can leave relevant questions unanswered. DDG can help provide a description of “strain-engineered 2D materials” in which Physical and Chemical properties are studied within the same footing.

Towards the end, I will touch upon recent works on two-dimensional tin. A so-called low-buckled structure leads to non-trivial topological effects. (This low-buckled structure is seen on silicene, germanene, and blue phosphorus.) In addition, a graphane-like fluorinated structure (i.e., fluorine atoms realizing a tetrahedral coordination) has been shown to bring the gap away from the K-points and onto the Gamma point [5,6].

Unfortunately, freestanding “stanene” is not the most stable two-dimensional phase of tin, and the most stable phase is not a viable material for topological fullerenes. Furthermore, three-dimensional fluorinated tin exists on common household products such as toothpaste, so it is stable under ambient conditions and easy to fabricate. There is no indication of tetrahedral coordination on bulk fluorinated tin, and the most stable 2D structure of fluorinated tin is not like the one predicted before either [5,6]. The actual optimal two-dimensional fluorinated phase is topologically trivial and it can provide a new material platform for spintronics in two-dimensions [7].

References:
  1. Discrete Differential Geometry. Bobenko et al. Birkhäuser (Basel); 2008.
  2. Sloan et al. PRB 87, 155436 (2013).
  3. Pacheco SanJuan et al. PRB 89, 121403(R) (2014).
  4. Pacheco SanJuan et al. ACS Nano 8, 1136 (2014).
  5. Ma et al. J. Phys. Chem. C 116, 21977 (2012).
  6. Xu et al. PRL 111, 136804 (2013).
  7. Rivero et al. Submitted for publication on July 28, 2014.

Oklahoma State Physics Department

Seminars and Colloquia, November 10-14, 2014


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Speaker:Dr. Brad K. Abbott
Homer L. Dodge Department of Physics & Astronomy
University of Oklahoma
Date:Thursday, November 13, 2014
Time:1:30 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Title:Heavy Flavor Physics

Joint Chemistry and Physics Colloquium:

Speaker:Dr. Ken A. Dill
Director, Laufer Center for Physical and Quantitative Biology
Louis & Beatrice Laufer Endowed Chair of Physical and Quantitative Biology
Distinguished Professor, Departments of Physics and Chemistry
Stony Brook University
Date:Thursday, November 13, 2014
Time:3:30 PM
Place:PS 103
Title:Proteins are the Original Programmable Self-Assembling Nano-Machines

Abstract:

Protein molecules perform tens of thousands of different functions at the nano-scale.  There has been considerable progress over the past 50 years on the “Protein Folding Problem”, the question of how a polymer sequence can encode its structure.  The current frontier is in how protein structures can encode their microscopic mechanisms.  I will describe some progress on the conceptual, modeling and simulational aspects of these questions, and progress on synthesizing non-biological foldamers that can mimic some properties of proteins.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Rebecca Flint
Department of Physics & Astronomy
Iowa State Unversity
Date:Friday, November 14, 2014
Time:2:30 PM
Place:Room 103, Nielsen Hall, OU
Title:Hidden (Hastatic) Order in URu2Si2

Abstract:

The development of collective long-range order occurs by the spontaneous breaking of fundamental symmetries, but the broken symmetry that develops below 17.5K in the heavy fermion material URu2Si2 has eluded identification for over twenty five years—while there is clear mean-field-like specific heat anomaly, the absence of any large observable order parameter has given the problem the name “hidden order.”

In this talk, I will show how the recent observation of heavy Ising quasiparticles in the hidden order phase provides the missing puzzle piece. To form Ising quasiparticles, the conduction electrons must hybridize with a local Ising moment—a 5f2 state of the uranium atom with integer spin. As the hybridization mixes states of integer and half-integer spin, it is itself a spinor and this “hastatic” (hasta: [Latin] spear) order parameter therefore breaks both time-reversal and double time-reversal symmetries. A microscopic theory of hastatic order naturally unites a number of disparate experimental results from the large entropy of condensation to the spin rotational symmetry breaking seen in torque magnetometry. Hastatic order also has a number of experimental consequences, most notably a tiny transverse magnetic moment in the conduction electrons.


Oklahoma State Physics Department

Seminars and Colloquia, November 17-21, 2014


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Speaker:Dr. Wade C. Fisher
Department of Physics and Astronomy
Michigan State University
Date:Thursday, November 20, 2014
Time:1:30 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Title:Putting a Spin on the Fate of the Vacuum

Abstract:

The discovery of the Higgs boson has been hailed as a historic triumph of quantum field theory and has given the field physics new insight into the nature of our universe. This successful connection of theory prediction and experimental discovery seems like serendipity, but the story does not appear to be complete. Measurements of Higgs boson properties have thus far been in agreement with predicted values, but many questions remain. The mass of the Higgs boson itself is an excellent indicator of new physics, as it is too heavy to explain electroweak precision measurements and too light to maintain a stable vacuum. This presentation will review the state of Higgs property measurements and the efforts in place to learn more.


Physics Colloquium:

Speaker:Dr. Wade C. Fisher
Department of Physics and Astronomy
Michigan State University
Date:Thursday, November 20, 2014
Time:3:30 PM
Place:PS 110
Title:Horror Vacui — The Higgs Boson and the Fate of our Vacuum

Abstract:

Predicted five decades ago, the Higgs mechanism provides a means to explain the origin of elementary particle masses. This mechanism suggests that the quantum vacuum is filled with a fluctuating condensate of Higgs bosons, with which particles interact to gain mass. The recent discovery of the Higgs boson has been hailed as a historic triumph of quantum field theory and has given the field of physics new insight into the nature of our universe. This successful connection of theory prediction and experimental discovery seems like serendipity, but the story does not yet appear complete. Measurements of Higgs boson properties have thus far yielded good agreement with predicted values, but many questions remain. The mass of the Higgs boson itself is an excellent indicator of new physics, as it is too heavy to properly explain electroweak precision measurements and too light to maintain a stable vacuum. This presentation will introduce the questions behind particle physics’ newest discovery and explore the possible paths the future of Higgs boson physics may entail.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.


OU/OSU Condensed Matter Physics Seminar:

Speaker:Dr. Elias D. Towe
Department of Electrical and Computer Engineering
Carnegie Mellon University
Date:Friday, November 21, 2014
Time:11:30 AM
Place:Room 420 Devon Energy Hall, OU
Title:Transition-Metal Dichalcogenides: Another Two-Dimensional Materials System that is Different from Graphene

Abstract:

Transition-metal dichalcogenides are layered semiconductor materials with a hexagonal crystal structure. One of their main attractions to the semiconductor community is that, unlike graphene, they have a band gap. This talk will present some structural and optical characterization of a few representative members of this class of materials (molybdenum disulfide, tungsten diselenide, and molybedum diselenide). Even though the materials are only a few nanometers thick, they have a number of interesting characteristics that might be useful for certain applications. We will discuss one of these characteristics: dependence of the band gap on applied external electric stress. The variation of the band gap with electric stress is potentially of use in electronic and photonic devices. In photonics, it could enable spectrally agile devices for communications and imaging.


Oklahoma State Physics Department

Seminars and Colloquia, November 24-28, 2014


Thanksgiving Break: No Wednesday classes, Thursday-Friday University Holiday.


Oklahoma State Physics Department

Seminars and Colloquia, December 1-5, 2014


Prefinals Week


Special Physics Seminar:

Speaker:Dr. Paul D. Lett
Quantum Measurement Division
National Institute of Standards and Technology (NIST), Gaithersburg, MD
Date:Wednesday, December 3, 2014
Time:1:30 PM
Place:PS 103
Title:Making Light Fast While the Information Stays Not-So-Fast

Abstract:

We know how to make “fast light” where the group velocity is clearly superluminal and pulses are clearly advanced.  We also know that if information travels superluminally problems with causality arise.  I review “fast light” mechanisms as well as our investigations of the physical mechanisms that keep the information in fast light beams causal.  I will present some recent experiments that look at how quantum information is degraded by dispersive media, and some interesting differences between fast and slow light in this context.

Note: The student-speaker question/answer session will be at 2:30–3:00 PM in room PS 147 PSII.


Oklahoma High Energy Physics Seminar on Talk-Back Television:

Speaker:Dr. Bariş Altunkaynak
Homer L. Dodge Department of Physics & Astronomy
University of Oklahoma
Date:Thursday, December 4, 2014
Time:1:30 PM
Place:106 B Studio Room, Classroom Building, OSU
& Nielsen Hall, Room 103, OU
Title:Flavor Changing Heavy Higgs Interactions at the LHC

Oklahoma State Physics Department

Seminars and Colloquia, December 8-12, 2014


Finals Week


Oklahoma State Physics Department

Seminars and Colloquia, December 15-19, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, December 22-26, 2014


No talks scheduled


Oklahoma State Physics Department

Seminars and Colloquia, December 29-31, 2014


No talks scheduled


Last Updated:

jhhp@jperk.phy.okstate.edu