PHYSICS COLLOQUIUM SCHEDULE
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Refreshments will be served starting at 3:15 PM in NPB 2205 Department of Physics Colloquium Committee: Hebard (Chair), Fry, Furic, Mitselmakher, Obukhov, Ramond (members) |
AUGUST 24 |
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| Speaker | Graduate Student Meeting with Dr. Xiaoguang Zhang 4:00pm in 1002 NPB | |
August 31 |
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| Speaker | Amlan Biswas, UF Physics | |
| Title | Magnetoelectrism in crystals | |
| Abstract | A discussion of the magnetic properties of matter usually addresses the effect of magnetic fields on magnetization. While the effect of an electric field on magnetism is also firmly established, we are much more familiar with the equation M = χmH than with M=αE, where χm is the magnetic susceptibility and α quantifies the magnetoelectric effect. A reason for this unfamiliarity is that α is negligible for most magnetic materials. I will discuss the origin of the magnetoelectric effect in materials and why the effect is small in single phase materials. I will describe our experiments on three materials from the perovskite family: LaPrCaMnO3, BiMnO3, and SrTiO3 and the unexpectedly large magnetoelectric coupling we observed under certain conditions. Ongoing experiments in our research group have been designed to fabricate and study these materials and further enhance their magnetoelectric properties. | |
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SEPTEMBER 7 |
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| Speaker | James Hamlin, UF Physics | |
| Title | The expanding role of compressed matter in superconductivity research | |
| Abstract | Measurements at low temperature are a standard part of the characterization of newly discovered materials. Due to their technical difficulty, measurements under high pressure conditions are not nearly as ubiquitous. Consequently, the vast majority of materials have yet to be characterized under pressure. The recent discoveries of high-temperature superconductivity in compressed iron selenide and hydrogen sulfide hint that many exciting discoveries still await in the unexplored high-pressure phases of otherwise well-studied materials. In this talk, I will provide an overview of results obtained using a new apparatus that combines designer diamond anvils with automated pressure measurement and application in order to to rapidly locate and characterize pressure induced phase transitions. Using elemental barium metal as an example, I will also present work using this apparatus to examine superconductivity in metastable structures obtainable only by varying pressure under cryogenic conditions. Finally, I will discuss an ongoing collaborative effort which combines synthesis, high pressure measurements, and high-throughput computation with the aim of accelerating the discovery of pressure-induced superconductors. | |
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SEPTEMBER 14 |
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SEPTEMBER 21 |
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| Speaker | Tim Sumner (Imperial College) | |
| Title | Celestial Dynamics: The Mystery Deepens | |
| Abstract | The mid-1980s saw the birth of many dedicated direct dark matter search experiments, starting up as a result of the mounting evidence for enhanced gravitational potentials in a number of astrophysical systems, and in the light of many particle-physics frameworks predicting new (suitable) particles. These experiments and indeed many other indirect search experiments have made solid progress since then but still we lack any definitive evidence. Meanwhile there has been interesting growth in alternative gravity scenarios, but also leaving us without a clear solution. This talk will review the situation and look forward to what the future might hold with new experiments and new types of observation. | |
| Host | Mueller | |
SEPTEMBER 28 |
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| Speaker | Klaus Honscheid, The Ohio State University | |
| Title | Probing the Accelerating Universe with the Dark Energy Survey | |
| Abstract | Why is the expansion of the universe speeding up? Is cosmic acceleration due to dark energy or does it require a modification of General Relativity? If it’s due to dark energy, is it the energy density of the vacuum (Einstein's cosmological constant) or something else? To address these questions, the Dark Energy Survey (DES) collaboration built the 570-megapixel Dark Energy Camera for the Blanco 4-meter telescope at NOAO's Cerro Tololo Inter-American Observatory in Chile, to carry out a 5-year, deep, multi-band, optical survey of several hundred million galaxies and several thousand supernovae. The DES survey began in 2013 and recently started the fifth and final observing season. In this talk I will highlight recent results and discuss how DES is measuring the history of cosmic expansion and the growth of structure using complementary techniques including the large-scale galaxy distribution and weak gravitational lensing of the light emitted by 26 million distant galaxies. | |
| Host | Darin Acosta | |
OCTOBER 5 |
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| Speaker | Vivien Zapf, NHMFL | |
| Title | New path to multiferroic behavior | |
| Abstract | Multiferroics are materials where magnetism and ferroelectricity coexist and possibly couple to each other. Research is driven by the intriguing interplay of spin, charge and lattice, as well as potential applications since they lower power consumption compared to spintronics by several orders of magnitude. To date, multiferroic research has focused on inorganic materials such as oxides. However a growing research effort is devoted to classes of materials that combine magnetic ions with organic ligands, such as metal-organic frameworks and molecular magnets. These materials offer different mechanisms for both magnetism and ferroelectricity and can have significant coupling between them due to the soft lattices. In particular, I will present a new result on creating multiferroic behavior using a spin state transition. Whereas in conventional magnetic order, the spin directions spontaneously form patterns, in spin state transitions, the total spin of the 3d magnetic ion changes due to a change in the occupation of partially-filled d orbitals. Spin state transitions can be strongly-coupled 1st order phase transitions driven by temperature, magnetic field, pressure, or other tuning parameters. Spin-state transitions can occur up to room temperature at ambient pressures in 3d transition metal-organic systems. Here, we demonstrate that these spin state transitions can lead to multiferroic behavior in a molecular magnetic materials. | |
| Host | Art Hebard | |
OCTOBER 12 |
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OCTOBER 19 |
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| Speaker | Postponed to October 26 | |
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OCTOBER 26 |
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| Speaker | Chris Lobb (University of Maryland) | |
| Title | Ohm’s Law and Beyond for Atom Circuits | |
| Abstract | Atomtronics is an emerging interdisciplinary field that is creating new devices and circuits where ultracold atoms, often in the superfluid state, have a role analogous to that of electrons in electronics. After giving a brief overview of some experimental neutral atom-circuit results, I will show how these results can be described by lumped-element models analogous to those used in electronics. Resistance, capacitance and inductance can be defined for neutral-atom circuits, and they are analogous to the Sharvin resistance (in the non-superfluid case), quantum capacitance, and kinetic inductance, respectively, in electronic circuits. In the superfluid case, quantum coherence leads to behavior analogous to superconducting quantum interference devices (SQUIDs) and vortex-induced resistance. In collaboration with R. B. Blakestad, G. K. Campbell, C. W. Clark, S. Eckel, M. Edwards, K. Helmerson, W. T. Hill, III, F. Jendrzejewski, J. G. Lee, B. J. McIlvain, S. R. Muniz, N. Murray, W. D. Phillips, A. Ramanathan, K. C. Wright, and M. Zelan. | |
| Host | Art Hebard | |
NOVEMBER 2 |
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| Speaker | Corene Matyas, UF Department of Geography | |
| Title | Hurricanes: from formation to landfall | |
| Abstract | Tropical cyclones require specific dynamic and thermodynamic conditions to form, and those conditions have been present over much of the Atlantic Basin during the 2017 hurricane season. This presentation begins by discussing these conditions and illustrates them using examples from Hurricanes Harvey and Irma as they were discussed during the hurricanes course that I teach during fall semesters. In the second part of the presentation, I present an overview of my research that examines the spatial distribution of rainfall regions as tropical cyclones approach and move over the United States. The first study examines climatological rainfall and wind patterns for landfalls occurring during 1948-2014. The second study measures the radial and azimuthal distribution of rainfall according to radar data and illustrates how the evolution of rainfall after landfall corresponds to interaction with the relatively dry continental air mass, de-intensification, and proximity to frontal boundaries. This research is sponsored by a CAREER Award from the National Science Foundation. | |
| Host | Pierre Ramond | |
NOVEMBER 9 |
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| Speaker | Shane Larson, CIERA, Northwestern University | |
| Title | Probing the Stellar Graveyard: Gravitational waves from ultra-compact binaries | |
| Abstract | The population of ultra-compact binaries in the Milky Way encodes a fossil record of stellar evolution in the galaxy. Taken as a population, the distributions of stellar types, orbital parameters, and masses encodes the signatures of processes that drive the evolution of these systems, including common envelope phases and epochs of mass transfer. LISA is a planned gravitational wave interferometer in space, a million times larger than their ground-based counterparts. The enormous size makes LISA sensitive to orbital periods in the range of hundreds to tens of thousands of seconds, a regime populated by binary systems comprised of white dwarfs, neutron stars, and black holes. All told, there should be some 10 million such systems in the Milky Way, providing an ample discovery space to map out and characterize these sources. In this talk we'll discuss LISA observations of the ultra-compact binary population. We'll discuss current work that illustrates how to use population synthesis to model the galaxy, and examine recent work that shows how joint gravitational wave and electromagnetic observations can constrain mass transfer processes in these systems. | |
| Host | Guido Mueller | |
SPECIAL COLLOQUIUM - FRIDAY, NOVEMBER 17 |
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| Speaker | Dan Green, Fermilab | |
| Title | Fermilab and the Foundations of the Standard Model | |
| Abstract | Fermilab has been a leader in the exploration of the Standard Model throughout its 50 year history. The past history will be reviewed. The present, with international collaboration between the U.S. and CERN, exploration beyond the SM (BSM) is the future with FNAL and DUNE and CERN and the high luminosity LHC (HL LHC). | |
| Host | Darin Acosta. | |
NOVEMBER 30 |
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| Speaker | Robert Brandenberger, McGill University | |
| Title | Testing String Theory with Cosmological Observations | |
| Abstract | Current paradigms of early universe cosmology suffer from a number of conceptual problems. I will explore the possibility that superstring theory could lead to a new scenario of the very early universe, and that this scenario could be tested with cosmological observations." | |
| Host | Richard Woodard | |
PHYSICS COLLOQUIUM SCHEDULE |
Spring 2018 |
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The
Colloquia are in Room 1002 NPB on Thursday
at 4:05 PM
Refreshments will be served starting at 3:15 PM in NPB 2205 Department of Physics Colloquium Committee: Hebard (Chair), Fry, Furic, Mitselmakher, Obukhov, Ramond (members) |
JANUARY 11 |
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| Speaker | Steve Kivelson (Stanford University) | |
| Title | Intertwined Order in Highly Correlated Electron Fluids | |
| Abstract | Using the cuprate high temperature superconductors as the best studied illustrative example, I will discuss the question - Why are the phase diagrams of highly correlated electronic systems so complicated? | |
| Host | Peter Hirschfeld | |
JANUARY 18 |
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| Speaker | reserved for a faculty search candidate | |
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JANUARY 25 |
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| Speaker | reserved for a faculty search candidate | |
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FEBRUARY 1 |
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| Speaker | reserved for a faculty search candidate | |
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FEBRUARY 8 |
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| Speaker | reserved for a faculty search candidate | |
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FEBRUARY 15 |
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| Speaker | reserved for a faculty search candidate | |
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FEBRUARY 22 |
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| Speaker | reserved for a faculty search candidate | |
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MARCH 1 |
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| Speaker | reserved for a faculty search candidate | |
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MARCH 8 |
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| Speaker | APS meeting and spring break | |
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MARCH 15 |
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| Speaker | reserved for a faculty search candidate | |
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March 22 |
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| Speaker | reserved for a faculty search candidate | |
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March 29 |
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| Speaker | Barry Barish, Caltech | |
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| Host | Guenakh Mitselmakher | |
April 5 |
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| Speaker | Reserved for a faculty search candidate/td> | |
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APRIL 12 |
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| Speaker | Nadya Mason (UIUC) | |
| Title | Designing Superconductivity: Manipulating Interactions in Arrays of Superconducting Islands | |
| Abstract | One of the most fundamental questions in physics is how the macroscopic properties of matter emerge from microscopic constituents. Often, complex electronic correlations at the micro-scale act to create remarkable macroscopic materials properties, such as superconductivity and ferromagnetism. But the parameters relevant to understanding and manipulating these correlations are difficult to access. In this talk, I will discuss a “bottom-up” approach to studying collective effects in matter via nanostructured arrays of superconducting islands. We fabricate large arrays of superconducting islands patterned on normal metal films; by changing the size and configuration of the islands, we can to tune the parameters relevant to 2D superconductivity, such as disorder, dissipation, and phase separation. I will discuss electrical transport measurements of these systems, including characterization of the superconducting transitions, vortex dynamics in finite magnetic-fields, and evidence that the system approaches an unusual metallic ground state as the island spacing is increased. I will also discuss the mechanism behind the suppression of superconductivity in individual granular islands, even at large diameters. | |
| Host | Amlan Biswas | |
APRIL 19 |
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| Speaker | Reserved for a faculty search candidate | |
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