Events at Physics |
Events During the Week of February 8th through February 15th, 2015
Monday, February 9th, 2015
- Plasma Physics (Physics/ECE/NE 922) Seminar
- The tokamak density limit: a thermo-resistive disruption mechanism
- Time: 12:00 pm - 1:00 pm
- Place: 1610 Engineering Hall
- Speaker: Dr. David Gates, Princeton Plasma Physics Laboratory
- Host: UW
- R. G. Herb Condensed Matter Seminar
- Faculty Candidate Seminar
- Surface Plasmons and Impurity States in Graphene
- Time: 4:00 pm
- Place: 4272 Chamberlin Hall
- Speaker: Victor Brar , California Institute of Technology
- Abstract: Graphene, an atomically thin sheet of carbon atoms, provides a unique platform to study quasiparticle interactions and to create optical metamaterials with novel properties. The 2D nature and linear band structure of graphene give rise to a semi-metal behavior, with tunable dielectric properties and a high electron mobility. In the DC regime, these properties allow graphene to display novel screening behavior in the presence of charged impurities, which I will show can be probed directly using scanning tunneling spectroscopy (STM). At optical (mid-IR) frequencies, the graphene dielectric function is strongly perturbed by the presence of collective excitations known as surface plasmon polaritons (SPPs), which are optical modes - supported by free carriers - that are bound to the graphene sheet. These modes show a number of remarkable properties, including a carrier density dependent dispersion relation, and wavelengths that are more than 100 times shorter than freespace. I will show how the surface plasmons in graphene can be harnessed to create infrared metasurfaces that have tunable optical properties. These materials will be shown to exhibit extreme light-matter interactions that can control the macroscopic absorption and emission properties of nanostructured dielectric stacks.
- Host: Coppersmith
Tuesday, February 10th, 2015
- Chaos & Complex Systems Seminar
- Energy and ecosystems: Howard Odum's seminal 1973 paper, "Energy, ecology, and economics," 42 years later
- Time: 12:05 pm - 1:00 pm
- Place: 4274 Chamberlin Hall (Refreshments will be served)
- Speaker: Bill Fischer, Agronomy, Business, Law, and Psychiatry
- Host: Clint Sprott
Wednesday, February 11th, 2015
- R. G. Herb Condensed Matter Seminar
- Faculty Candidate Seminar
- Dynamical signatures and applications of many-body localization
- Time: 4:00 pm - 5:00 pm
- Place: 4274 Chamberlin
- Speaker: Sarang Gopalakrishnan, Harvard University
- Abstract: The many-body localization (MBL) transition in isolated quantum systems is
a transition at which equilibrium statistical mechanics breaks down; the
resulting localized phase has extensively many local conserved quantities
and acts as a quantum memory. In this talk, I consider experimentally
feasible probes of the MBL phase, such as a.c. conductivity, polarization
decay, and the response to spin echo protocols, and show that these probes
give clear signatures of MBL that distinguish it from single-particle
localization, even in realistic systems that are only imperfectly isolated
from the environment. I then turn to the regime near the MBL transition,
and show that low-frequency response in this regime exhibits is dominated
by rare-region effects, which can be described using "Griffiths"
arguments. Finally, I comment on how the absence of intrinsic decoherence
in the localized phase can be used as a resource for quantum information
science. - Host: Coppersmith
Thursday, February 12th, 2015
- Astronomy Colloquium
- Dynamical Structure in the Galactic disk -- a new Decade of Galactic Discovery
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall
- Speaker: Alice Quillen, Univeristy of Rochester, Astronomy & Astrophysics
- Abstract: Soon GAIA observations will increase our knowledge of the positions and velocities of millions of stars in the our Galaxy.
I will explore how star formation, spiral structure, perturbations and remnants from dwarf galaxies, and the Galactic bar cause substructure in local stellar velocity distributions.
I will discuss challenges in better measuring the shape and stellar distribution of the Milky Way, understanding dynamical processes in the disk and its formation and past evolution. - Host: Prof Elena D'onghia
- R. G. Herb Condensed Matter Seminar
- Faculty Candidate Seminar
- Spin orbit interaction induced magnetic dynamics
- Time: 4:00 pm - 5:00 pm
- Place: 474 Chamberlin Hall
- Speaker: Luqiao Liu, IBM TJ Watson Research Center
- Abstract: Controlling magnetic orientation in a fast and energy-efficient way is both fundamentally important and has profound technical implications. Conventional ways of switching magnetic moment include employing magnetic fields from current-carrying coil and using the spin transfer torque effect from spin valve structures. Recent studies show that spin orbit interaction induced phenomena, such as the spin Hall effect and spin momentum locking in topological insulators, can provide effective mechanisms to generate spin currents and to control the orientation of nano-magnets. In this talk, I will discuss various magnetic dynamics that can be excited using spin orbit interactions, including ferromagnetic resonance, reversible magnetic switching and persistent magnetic oscillations. Compared with conventional spin torque devices, a higher current-spin conversion efficiency and lower energy dissipation are exhibited in those experiments. Besides, I will also talk about experimental approaches that can be utilized to identify the origin and quantify the strength of those effects. With the information gained in those studies, further improvement on the spin generation efficiency can be expected.
- Host: Coppersmith
Friday, February 13th, 2015
- 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
- Physics Department Colloquium
- Special Colloquium presented by WARF
- WARF on Campus
- Time: 3:30 pm - 4:30 pm
- Place: 2241 Chamberlin Hall
- Speaker: Rafael Diaz, Licensing Associate, Wisconsin Alumni Research Foundation
- Abstract: WARF management and staff will discuss the following topics:
- WARF overview and WARF’s role in securing and commercializing IP, presented by Leigh Cagan, Chief Technology Commercialization Officer
- Protecting innovation: the process of invention disclosure and patenting, presented by Stephanie Whitehorse, Intellectual Property Professional
- Technology commercialization: incubation, licensing, and startups, presented by Chris Thomas, Licensing Professional
- Current hot topics: Stanford v. Roche, external collaborations, patent reform, presented by Michael Falk, General Counsel