Physics Department Colloquium Schedule

Default Location: 101 UPL (Richards Bldg) Default Time: Thursday at 3:45 PM Refreshments: 3:15 PM unless otherwise indicated Note: Link to Maps of FSU Campus and Vicinity
Date	Description
January
17	Speaker: Siegfried S. Hecker, Stanford University (Host: Gregory Boebinger) Title: Plutonium: From Mott transitions to the bomb Abstract: Plutonium can electrify the world or it can destroy it. Regardless of its societal implications, it is the most complex and fascinating element in the periodic table. Its 5f electrons sit at a knife-edge between being itinerant or localized, thereby creating a highly unstable, temperamental element whose most intriguing properties I will highlight. I will also describe some of my international scientific adventures dealing with plutonium from how we cope with its complex aging characteristics in the U.S. nuclear weapons stockpile, to my visits to North Koreas plutonium complex, and how I worked with former Russian nuclear adversaries to keep plutonium out of the hands of terrorists in places like Kazakhstan. Special Note: Mott Lecture
24	Speaker: Michael Turner, University of Chicago (Host: Todd Adams) Title: The Big Mysteries of Cosmology Abstract: Deep connections between the very large -- the cosmos -- and the very small -- quarks -- have shaped the Universe we see today and entangled the agendas of particle physics and cosmology. I discuss the present state of cosmology and the big mysteries that point to new physics -- dark matter, dark energy, inflation and the baryon asymmetry of the Universe -- and the prospects for progress. Special Note: Lannutti Lecture
31	Speaker: Stefan Westerhoff, University of Wisconsin-Madison (Host: Todd Adams) Title: The Search for the Origin of Cosmic Rays with IceCube Abstract: Cosmic rays are relativistic charged particles incident on the Earthʼs atmosphere from outer space. They have been detected with energies that range over more than 12 orders of magnitude and extend to tens of joules per particle, making them the highest energy particles ever observed. More than a hundred years after their discovery, their origins remain a mystery. Only extreme astrophysical environments, such as supernova remnants or the hot, dense surroundings of supermassive black holes, are likely to be able to accelerate particles to such energies. By observing cosmic rays, and their nuclear decay products (gamma rays and neutrinos), we hope to learn where and how cosmic rays are accelerated and thus open a new window in astronomy. With a new generation of neutrino, gamma-ray and cosmic-ray detectors, we are now accumulating data sets of unprecedented size and quality. One of these instruments is the IceCube detector at the South Pole, completed in 2010. While primarily built to detect neutrinos from astrophysical sources, IceCube is also a very sensitive cosmic-ray detector. In this talk, I will report on new IceCube results on the energy spectrum and the arrival direction distribution of Galactic cosmic rays in the energy range from TeV to several hundred PeV.
February
7	Speaker: Alexander Volya, Florida State University (Host: Mark Riley) Title: The nuclear many-body problem near the limits of stability. Abstract: The atomic nucleus is a natural self-binding quantum many-body system where structure and stability are governed by an intricate interplay of quantum many-body interactions and the dynamics of the nuclear reaction continuum. In my presentation I will discuss the physics of decays and reactions involving unstable nuclei. I will demonstrate how a consistent simultaneous description of many-body structure and reactions can help with fundamental questions in nuclear science, astrophysics, physics of the Standard Model, and in general quantum many-body physics.
14	Speaker: Kristen Buchanan, Colorado State University (Host: Susan Blessing) Title: Spin Dynamics in Patterned Magnetic Structures Abstract: Dynamic processes in magnetic materials are important from a fundamental and applied perspective alike. Dynamic processes can be used to measure important material properties, offer opportunities for the development of new devices based on spin waves, and, furthermore, can be used as a means to probe the nature of spin transfer torque effects. This talk will touch on each of these areas. I will discuss measurements of thermal spin waves using Brillouin light scattering (BLS) that were used to determine the magnetic exchange constant for soft FeCo films of high magnetization, materials that are an integral part of todays magnetic recording heads. On smaller length scales, BLS microscopy provides new opportunities to map out and understand both propagating and standing spin wave excitations in nano-patterned magnetic films. Confinement in nanomagnets alters their energetics, and consequently affects the dynamic properties of the system. Furthermore, at low magnetic fields it leads to new magnetic states, for example, magnetic vortices and antivortices that, in turn, exhibit unique dynamic properties. Finally, I will show how the motion of a magnetic vortex in a patterned magnetic thin film has the potential to provide a means to provide a quantitative measure of the relative contributions of adiabatic and non-adiabatic spin torque effects via the shape of its dynamic trajectory.
28	Speaker: Charles Kane, University of Pennsylvania (Host: Nicholas Bonesteel) Title: From Topological Insulators to Majorana Fermions Abstract: A topological insulator is a material that is an insulator on its interior, but has special conducting states on its surface. These surface states are unlike any other known two dimensional conductor. They are characterized by a unique Dirac type dispersion relation and are protected by a topological property of material's underlying electronic structure. Topological insulators have attracted considerable interest as a fundamentally new electronic phase with applications from spintronics to quantum computing. In this talk we will outline the theoretical discovery of this phase and describe experiments that have observed its signatures in both two and three dimensional electronic systems. We will close by arguing that the proximity effect between an ordinary superconductor and a topological insulator leads to a novel interface state that may provide a new venue for observing a Majorana fermion and for realizing proposals for topological quantum computation.
March
7	Speaker: Peter Fischer, Lawrence Berkeley National Laboratory (Host: Steve Hill) Title: Soft X-ray microscopy: Facing the mesoscale challenge in magnetism Abstract: Over the last decade magnetism research focused on a fundamental understanding and controlling spins on a nanoscale. A wealth of information has been achieved in this reductionists approach, which to a large extent was made possible by the development of advanced instrumentation targeting the nanoscale. Recently, it has been recognized, that the next step beyond the nanoscale will be governed by mesoscale phenomena [1], since those are supposed to add complexity and functionality, which are essential parameters to meet future challenges in terms of speed, size and energy efficiency of spin driven devices. The development and application of multidimensional visualization techniques, such as tomographic magnetic imaging and investigations of fast and ultrafast spin dynamics down to fundamental magnetic length and time scales with elemental sensitivity in emerging multi-component materials will be crucial to achieve mesoscience goals. Magnetic soft X-ray microscopy is a unique analytical technique combining X-ray magnetic circular dichroism (X-MCD) as element specific magnetic contrast mechanism with high spatial and temporal resolution [2]. Our approach is to use Fresnel zone plates as X-ray optical elements providing a spatial resolution down to currently 10nm [3] thus reaching out into fundamental magnetic length scales such as magnetic exchange lengths. The large field of view allows investigating both the complexity, but also the stochasticity of magnetic processes, such as nucleation or reversal. Utilizing the inherent time structure of current synchrotron sources fast magnetization dynamics such as current induced wall and vortex dynamics in ferromagnetic elements can be performed with a stroboscopic pump-probe scheme with 70ps time resolution, limited by the lengths of the electron bunches. In this talk I will review recent studies of magnetic vortex structures, where we found a stochastic character in the nucleation process, which can be described within a symmetry breaking DM interaction [4]. I will also present time resolved studies of dipolar coupled magnetic vortices, where we found an efficient energy transfer mechanism, which can be used for novel magnetic logic elements [5]. First attempts to image the 3dim magnetic domain structures in rolled-up Ni nanotubes are very promising. This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy under Contract No. DE-AC02-05-CH11231. [1] BESAC report: From Quanta to the Continuum: Opportunities for Mesoscale Science (2012), http://science.energy.gov/~/media/bes/pdf/reports/files/OFMS_rpt.pdf [2] P. Fischer, Materials Science & Engineeering R72 81-95 (2011) [3] W. Chao, P. Fischer, T. Tyliszczak, S. Rekawa, E. Anderson, P. Naulleau, Optics Express 20(9) 9777 (2012) [4] M.-Y. Im, P. Fischer, Y. Keisuke, T. Sato, S. Kasai, Y. Nakatani, T. Ono, Nature Communications 3 983 (2012) [5] H. Jung, K.-S. Lee, D.-E. Jeong, Y.-S. Choi, Y.-S. Yu, D.-S. Han, A. Vogel, L. Bocklage, G. Meier, M.-Y. Im, P. Fischer, S.-K. Kim, NPG - Scientific Reports 1 59 (2011) Dr. Peter Fischer received his PhD in Physics (Dr.rer.nat.) from the Technical University in Munich, Germany in 1993 and his habilitation from the University in Wuerzburg in 2000 based on his pioneering work on Magnetic Soft X-ray microscopy. Since 2004 he is staff scientist and principal investigator at the Center for X-ray Optics within the Materials Science Division at Lawrence Berkeley National Laboratory in Berkeley CA. In 2012 he was appointed the lead-PI of the Magnetic Materials Program within MSD at LBNL. His current research program is focused on the use of polarized synchrotron radiation for the study of fundamental problems in nano- and mesoscale magnetism. He is involved in developing the scientific case for a next generation soft X-ray free electron laser at LBNL. Dr. Fischer has published 150+ peer reviewed papers and has given 220+ invited presentations at national and international conferences. For his achievements of hitting the 10nm resolution milestone with soft X-ray microscopy he was co-awarded with the Klaus Halbach Award at the Advanced Light Source in 2010. He was nominated a Distinguished Lecturer of the IEEE Magnetics Society in 2011.
14	Special Note: Spring Break!
21	Speaker: Shifeng Chen, University of Maryland School of Medicine (Host: Paul Eugenio) Title: Physics of Radiation Therapy: Fundamentals and Clinical Applications Abstract: As a branch of physics, medical physics is defined as application of physics to medicine and health care to diagnose and treat human diseases. One main branch of medical physics is radiation therapy physics, which utilizes the ionizing radiation to control or kill the cancer cells. Radiation therapy is one of three major modalities for cancer treatment, and it has been growing rapidly during last 20 years. Currently about two-thirds of cancer patients receive radiation therapy. This talk will include four parts: 1) overview of basic radiation biology for cancer treatment; 2) overview of fundamental physics of radiation therapy; 3) overview of modern radiation therapy technology; and 4) medical physics research.
28	Speaker: Edmund Myers, Florida State University (Host: Mark Riley) Title: Atomic mass measurement at the highest level of precision Abstract: J J Thomsons discovery of isotopes of neon in 1913 was the birth of atomic mass spectrometry. One hundred years later, atomic masses can be measured to a fractional precision of 0.1 parts per billion, many of these measurements having been carried out at Florida State. In this colloquium I will discuss how such precision atomic mass measurements are made, and their application to determining fundamental constants, precision tests of Quantum Electrodynamics, and neutrino mass.
April
11	Speaker: Undergraduate Poster Session (Host: Winston Roberts) Abstract: The Poster Session will provide a showcase for undergraduate research being carried out in the department. Posters will be available for viewing between 3:15 and 4:45. The poster session will also host competition for the Lannutti Undergraduate Research Award. This year, the Lannutti Undergraduate Research Award will consist of three cash awards in the amounts of $750, $500, and $250 for the top three posters presented at the Physics Undergraduate Research Poster Session on April 11, 2013. This poster session will be held at the regular Departmental Colloquium time on the 7th floor of the Keen Building.
18	Speaker: Christopher Gerardy, Florida State University (Host: Peter Hoeflich) Title: New Constraints on Thermonuclear Supernovae, or The Shapes of Things That Go Boom in the Night Abstract: Type Ia Supernovae are the thermonuclear explosions of compact White Dwarf stellar remnants in close binary star systems undergoing mass transfer. They have come into the spotlight as the premier tools for measuring cosmological distances and were the basis for the discovery of the accelerating expansion of the universe and the so-called ``dark energy. While there has been significant progress in our understanding of these objects there is still much that remains unknown about the details of these stellar explosions. Here at FSU we have been working to use a combination of cutting edge instrumentation and detailed model calculations to generate new observational diagnostics to probe the physics of Type Ia supernovae. In particular, near-infrared spectroscopy with the current and next-generation of large telescopes contains a wealth of new information about the conditions in the center of the progenitor star prior to thermonuclear runaway, and about the propagation of burning fronts in the earliest phase of the explosion. I will show results from our current studies using 8-m class telescopes to measure the densities and magnetic fields in progenitor stars and asymmetries in the early explosions. I will also comment on the prospects for using these tools in the next generation of instruments scheduled to come on-line in the next few years.
25	Special Note: Physics Department Awards Ceremony