Events at Physics
Events During the Week of March 18th through March 25th, 2012
- Condensed Matter Theory Group Seminar
- Quantum criticality of vanadium chains with strong relativistic spin-orbit interaction
- Time: 4:30 pm
- Place: 5310 Chamberlin
- Speaker: Natalia Perkins, UW-Madison
- Chaos & Complex Systems Seminar
- Rise and fall of a billion dollar molecule
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Olga Trubetskoy, UW Departments of Pharmacy and Comparative Biosciences
- Abstract: I will discuss a story of a aEurooebillion dollar moleculeaEuro that has been recently revisited on national drug discovery radar and will provide its less known links and direct connections to the history of local Madison biotech. The presentation will focus on overall complexity of drug response in humans including drug metabolism and toxicity on molecular, cellular, organismal and environmental levels including effects of some specific human factors and current personalized medicine approach.
- Host: Sprott
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin Hall
- R. G. Herb Condensed Matter Seminar
- Quantum and classical fluctuation phenomena in low-dimensional superconductors
- Place: CANCELLED
- Speaker: Victor Galitski, University of Maryland -- CANCELLED
- Abstract: Low-dimensional superconductivity provides a unique area in which a fascinating variety of novel and fundamental phenomena occur. In this talk, I will review recent theoretical and experimental work on superconducting fluctuation phenomena in low-dimensional superconductors. First, I will discuss unusual phases and fluctuation effects evident in the experimental studies of the field-tuned transition in two-dimensional disordered superconducting films and describe our theory of quantum superconducting fluctuations, which explains anomalous transport and thermal transport observed in the vicinity of the transition in these films. Next, I will focus on the recent experiment by the Penn State group [Wang et al., Nature Physics 6, 389 (2010)] on the long-range proximity effect in ferromagnetic nanowires proximity-coupled to superconducting electrodes. I will propose an explanation for both the anomalously-strong proximity effect and the mysterious resistance peak that preempts the superconducting transition in this experiment. In conclusion, I will discuss this and related setups involving ferromagnetic nanowires in the context of one-dimensional topological superconductors.
- Host: Vavilov
- Astronomy Colloquium
- TIdes and magnetic fields in Hot Jupiter Systems
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall
- Speaker: Evgenya Shkolnik, Lowell Observatory
- Abstract: Hot Jupiters, located only a few stellar radii from their parent stars, provide a laboratory in which we can study fundamental system parameters including planetary magnetic fields, a key component to understanding the planet's internal structure and atmospheric conditions. Over a dozen studies of hot Jupiter systems have independently converged on the same scenario: a short-period planet can induce activity on the photosphere and upper atmosphere of its host star, making the star itself a probe of its planet. This makes star-planet interactions (SPI) currently the most promising way to study exoplanetary magnetic fields. In addition, strong tidal interactions between the hot Jupiter and its star will increase the stellar rotation rate as well as the global stellar activity level, provided that the planet migrated early on in the system's history. Studying the tidal and magnetic interactions in such planetary systems builds our understanding of the formation, migration and evolution of close-in planets.
- Host: Ben Brown
- Theory Seminar (High Energy/Cosmology)
- Confronting Top AFB with Parity Violation Constraints
- Time: 2:00 pm
- Place: 5280 Chamberlin Hall
- Speaker: Ian-Woo Kim, University of Michigan
- Abstract: We consider the implications of low-energy precision tests of parity violation on t-channel mediator models explaining the top AFB excess measured by CDF and D0. Flavor-violating u-t or d-t couplings of new scalar or vector mediators generate at one-loop an anomalous contribution to the nuclear weak charge. As a result, atomic parity violation constraints disfavor at >3 sigma t-channel models that give rise to a greater than 20% AFB at the parton level for M_tt > 450 GeV while not producing too large a top cross-section. Even stronger constraints are expected through future measurements of the proton weak charge by the Q-Weak experiment.
- Physics Department Colloquium
- The quantum and classical properties of spins on surfaces
- Time: 3:30 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Andreas Heinrich, IBM Almaden Research Lab
- Abstract: The scanning tunneling microscope has been an extremely successful experimental tool because of its atomic-scale spatial resolution. In recent years this has been combined with the use of low temperatures, culminating in precise atom manipulation and spectroscopy with microvolt energy resolution. A cluster of magnetic atoms on a surface behaves similar to a classical magnetic particle: itaEuroTMs magnetization points along an easy-axis direction in space and magnetization reversal requires sufficient thermal energy to overcome a barrier. In this talk we will discuss how many atoms it takes to create such creates, which offers crucial insights into the size limits of stable magnetic nanoparticles. When the number of atoms becomes too small we observe quantum tunneling of magnetization aEuro" in the present case of the aEurooeclassicalaEuro Neel vector. Single atoms that are slightly decoupled from conducting substrates behave more like quantum mechanical entities. These can be studied with inelastic tunneling spectroscopy, a technique we coined spin-excitation spectroscopy. With this approach it is possible to measure the energy eigenstates of the quantum spin Hamiltonian that describes spins on surfaces with high precision. We will introduce its application to the measurement of the Zeeman energy, to magneto-crystalline anisotropy, and to spin-spin coupling via a superexchange interaction.
Dr. Andreas Heinrich Bio
Andreas Heinrich leads a research team at IBM's Almaden Research Center focused on exploring atomic-scale structures for possible applications in computation and datastorage. In January 2012 Heinrich and his team presented the worldaEuroTMs smallest magnetic data storage elements consisting of only 12 magnetic atoms. The work was published in the highest ranking scientific journal, Science, and widely reported in the media, including the New York Times. This work was based on a long-term research effort in HeinrichaEuroTMs team that started with the exploration of the magnetic properties of individual magnetic atoms on surfaces over ten years ago, highlighting IBMaEuroTMs commitment to long-term, exploratory research. Heinrich regularly gives invited lectures and seminars, including plenary lectures at leading international conferences. His main interest is in the exploration of the exciting world of atoms and structures built with atomic-scale precision and in educating the public on the amazing world of nanoscience. Heinrich is both a scientist and an engineer with a keen interest in advancing the experimental capabilities of state-of-the-art research tools. He and his team recently improved the time resolution of scanning tunneling microscopes aEuro" the mot advanced tool for atomic-scale studies on surfaces aEuro" by a factor of 1 million, another breakthrough paper published in Science in 2010. HeinrichaEuroTMs longer-term interest lies in the emerging field of quantum computation, where he hopes to demonstrate the use of single magnetic atoms on surfaces as qubits. Quantum computation has the potential to vastly improve computational performances of computers by taking advantage of the intriguing world of quantum mechanics that governs the properties of atoms. A native of Germany, Heinrich received his PhD in 1998 from the University of Goettingen in Germany and joined IBM in the same year as a postdoc in Dr. Donald EigleraEuroTMs team. Eigler is world-renowned for being the first person to reproducibly move individual atoms on surfaces, a tradition carried on proudly in HeinrichaEuroTMs research efforts.
- Host: Himpsel