This Week at Physics

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Events During the Week of February 16th through February 23rd, 2014

Sunday, February 16th, 2014

Wonders of Physics
Physics of Dimensions
Time: 1:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott and colleagues, UW Department of Physics
Abstract: The 31st annual presentation of the popular outreach program for the public. Advanced free tickets are recommended.
Host: Clint Sprott
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Wonders of Physics
Physics of Dimensions
Time: 4:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott and colleagues, UW Department of Physics
Abstract: The 31st annual presentation of the popular outreach program for the public. Advanced free tickets are recommended.
Host: Clint Sprott
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Monday, February 17th, 2014

Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
    http://cmb.physics.wisc.edu/journal/index.html
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (lzhang263@wisc.edu)
Host: Peter Timbie
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Tuesday, February 18th, 2014

Chaos & Complex Systems Seminar
Direct imaging of the nearest habitable planets
Time: 12:05 pm
Place: 4274 Chamberlin (refreshments will be served)
Speaker: Margaret Turnbull, Global Science Institute
Abstract: In the last twenty years, exoplanetary science has revolutionized the study of planetary systems and how they form -- and the next key goal motivating exoplanetary science is to discover and characterize exo-Earths. This talk will review (1) where we stand currently with habitable planet detection, (2) the reasons to attempt a direct imaging mission and the surprising multitude of factors that play into designing such a mission, and (3) what we could conceivably learn about life in the neighborhood of the sun with current and near-term technology. Although this young field has generated intense public interest and yielded thousands of surprising results, we may have barely scratched the surface of what the universe has to offer.
Host: Clint Sprott
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"Physics Today" Undergrad Colloquium (Physics 301)
The Early Universe
Time: 1:20 pm
Place: 2223 Chamberlin
Speaker: Peter Timbie, UW Madison Department of Physics
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Theory Seminar (High Energy/Cosmology)
Title to be announced
Time: 2:00 pm
Place: 5280 Chamberlin Hall
Speaker: Tim Linden, University of Chicago
Host: Jordi Salvadó Serra
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Faculty Candidate Seminar
Emerging spin-orbit interaction driven phenomena in magnetic heterostructures
Time: 4:00 pm
Place: 4274 Chamberlin Hall
Speaker: Xin Fan, University of Deleware
Abstract: Charge and spin are both intrinsic properties of electrons. While the charge property has been ubiquitously deployed in every electronic device, the potential of spin property is only realized since 1980s. The manipulation of spins in electronic devices, known as spintronics, has resulted in many practical applications. The first generation of spintronics devices, such as spin valves and magnetic tunnel junctions, uses the magnetization to tune the flow of electrons and has already revolutionized the development of computer hard disk drive. The new generation of spintronics devices uses electrons flow to control the magnetization. This electrical control on magnetization will lead to new generation of fast and nonvolatile magnetic random access memory. Such manipulation of magnetization becomes more feasible recently due to emerging spin-orbit interaction driven phenomena that arise from the interior of the materials as well as the interface in inversion symmetry-breaking heterostructures.
The Spin-orbit interaction is a relativistic effect describing the coupling between a particleaEuroTMs spin and motion. It lifts the spin-dependent degeneracy of electronaEuroTMs motion in a solid. The related phenomena have been intensively studied in semiconductors over the past decades. Very recently, it has been shown that the spin-orbit interaction in metals can be orders stronger than that in conventional semiconductors. It is demonstrated that an electric current through a heavy metal/ferromagnetic metal bilayer can efficiently control the magnetization of the ferromagnetic layer.
Although the phenomena have been successfully demonstrated, the microscopic detail of the spin-orbit interaction in the metallic bilayer is still unclear. The major question is whether the dominating spin-orbit interaction is from the spin Hall effect in the heavy metal itself (bulk effect) or the Rashba effect at the interface (interface effect). In this talk, I will firstly introduce both electrical and optical methods that I developed to determine the magnetic torques generated from the spin-orbit interaction. Then I will show the co-existence of interface and bulk contributions in the samples under study. The result suggests that both the selection of the heavy metal and the engineering of the interface are crucial for the control of the magnetization. In the end, I will discuss the challenges and potential researches in this area.
Host: Mark Eriksson/Peter Timbie
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Wednesday, February 19th, 2014

Physics Education Innovation Seminar
Undergraduate research: Garage Physics independent projects and ECE379 and Innovations in Physics 103 this Semester
Time: 11:00 am
Place: 5310 Chamberlin Hall
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Faculty Candidate Seminar
The Riddle of the Invisible Universe
Time: 4:00 pm
Place: 4274 Chamberlin Hall
Speaker: Matthew Szydagis, UC Davis
Abstract: The majority of the matter in our Universe does not shine in the form of the stars, nor is it even made up of atoms. This “dark matter” can be probed in experiments here on Earth, where it can scatter off nuclei, albeit rarely. I will discuss different technologies used in the quest for the Weakly Interacting Massive Particle (WIMP), a favorite dark matter candidate. Of special interest are the xenon-based detectors LUX (Large Underground Xenon) and LZ, its multi-ton-scale, next-generation successor. LUX has imposed the world’s strictest limit on the WIMP interaction probability across a wide range of WIMP masses, and disagrees with the potential WIMP detection claims of other experiments. I will also describe a complementary detection technique using small-scale bubble chambers. Lastly, I will present the landscape for the discovery potential for dark matter in the next decade.
Host: Sridhara Dasu/Albrecht Karle
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Thursday, February 20th, 2014

R. G. Herb Condensed Matter Seminar
Two- and three-dimensional spin liquid and interacting Majorana systems
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Zohar Nussinov, Washington University
Abstract: We examine the Hubbard model on pyrochlore-type lattices and illustrate how spin liquid features arise at a proximate exactly solvable point and its surroundings. We further introduce a framework for dualities and with its aid demonstrate that interacting Majorana nanowire systems as well as direction dependent Hubbard type and other general planar systems may display various critical and spin glass type phenomena.
Host: Natalia Perkins
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Astronomy Colloquium
"Four Problems in Trying to Form Galaxies(and how ISM Physics can Save US)"
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Desika Narayanan, Haverford College
Abstract: Building a comprehensive picture for the evolution of galaxies
from early times through present epoch requires understanding a huge dynamic range of physical processes. With observations ranging from detections of galaxies less than a billion years after the Big Bang to stellar and molecular cloud mass spectra in the Milky Way, the challenge has been to develop a concordance theory for galaxy formation than simultaneously explains this diverse range of observed galaxy properties across cosmic epoch. At the heart of many of the central questions in the astrophysics of galaxy evolution lies the physics of the interstellar medium, and galactic-scale star formation. In this talk, I will describe how understanding the complex interplay between small scale star formation physics and global galaxy evolution processes can lead to considerable insight in long-standing problems in both fields.<br>
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Host: Aleks Diamond-Stanic
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Friday, February 21st, 2014

Theory Seminar (High Energy/Cosmology)
A light Higgs boson from a composite Higgs theory
Time: 2:00 pm
Place: 5280 Chamberlin Hall
Speaker: Hsin-Chia Cheng, University of California, Davis
Abstract: TBA
Host: Jordi Salvadó Serra
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Physics Department Colloquium
Equilibrium and Driven Mesoscopic Dynamics in Complex Oxides
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Paul Evans, UW Materials Science & Engineering
Abstract: Complex oxide materials can exhibit a wide range of properties that are both fundamentally important and widely useful. The electrical polarization of complex oxide ferroelectrics is particularly interesting because the energetics of long-range interactions due to electrostatics and elasticity compete with much shorter-range interactions associated with the formation of defects and domain boundaries. This competition leads to a rich range of phenomena in nanoscale materials that are only now beginning to be explored. We describe a series of advances in experimental techniques based on the coherence and ultrafast time structure of synchrotron x-ray radiation that make it possible to explore the dynamics of these materials in a new regime. The competition of polarization and domain wall energies in nanoscale superlattices composed of alternating ferroelectric and dielectric layers of atomic-scale thicknesses leads to the formation of polarization domains. X-ray scattering show that these domains can be manipulated with applied electric fields and that the complex energy landscape leads to fluctuations in their configuration at room temperature. Future combinations of ultrafast time resolution and precise structural studies enabled by the spatial coherence of x-rays promise new insight into the dynamics of a wide range of other phenomena.
Poster: http://www.physics.wisc.edu/twap/posters/2014/3182.pdf
Video: http://www.physics.wisc.edu/vod/2014/02/21.html
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"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2014/2014-02-17.pdf

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