This Week at Physics

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Events on 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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