Events at Physics
Events on Thursday, November 12th, 2015
- R. G. Herb Condensed Matter Seminar
- Topological Quantum Matter
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Yong Chen , Purdue University
- Abstract: Topological quantum matter (TQM), where topological order or topological invariants are used to distinguish different phases of matter, has emerged as a major paradigm in condensed matter physics in recent years. TQMs feature topological bulk-boundary correspondences, where some nontrivial topologically-protected boundary modes are guaranteed to emerge due to the topologically nontrivial states in the bulk of the system. The first example of TQM is the well-known quantum Hall (QH) effect of two-dimensional electrons in a perpendicular magnetic field, where the bulk is insulating due to energy gaps from Landau level formation, and topological conduction free of backscattering occurs via chiral edge states, giving rise to quantized Hall conductance in units of e2/h that is now used as a quantum metrology to help define “ohm” or the even Planck constant itself. The list of TQMs has dramatically expanded in the past decade to now include new states of matter such as topological insulators (TI), which can be a generalization of the QH states to three dimensions and zero magnetic field due to the presence of strong spin orbit coupling (SOC), giving rise to a gapped insulator in the bulk and conducting spin-helical Dirac fermions on the surface promising for spintronics and other applications; topological semimetals, which realize 3D Dirac or Weyl fermions that can exhibit a condensed matter version of the “chiral anomaly”; topological superconductors, which could host quasiparticle analogues of “majorana fermions” potentially useful as qubits for “topological” quantum computation. While so far mostly studied for electronic systems, it is also possible to engineer “synthetic” gauge fields or SOC that may help realize analogous or new kinds of TQMs for photons or neutral atoms. This talk will overview some of the key physics and promised device applications, and describe efforts in my group to make, improve and characterize TQMs --- a particular focus in the past few years has been to realize truly intrinsic TIs that demonstrate salient signatures of “topological” transport, such as a thickness independent conductance in thin films, “half-integer” Dirac fermion QH effects and helical spin polarized current characteristic of topological surface states (TSS), and a “half-integer” Aharonov-Bohm effect when such TSS are confined in a (cylindrical) curved space. Such TIs could also be used as a starting point to make topological semimetals and superconductors.
- Host: McDermott
- Astronomy Colloquium
- The Kepler Cluster Study: Planets and Gyrochronology
- Time: 3:30 pm
- Place: 4421 Sterling Hall, Talk starts at 3:45 PM
- Speaker: Soren Miebom, Harvard CfA
- Abstract: The precise time-domain observations from NASA's Kepler mission have lead to a breakthrough in the search for exoplanets in star clusters and have begun a new era in the study of stellar rotation. The Kepler Cluster Study (KeCS) was implemented as part of the Kepler mission to search for transiting exoplanets in open star clusters and to study the dependencies of stellar rotation on the most fundamental stellar properties - age and mass. In this talk I will motivate the two primary goals of KeCS, present
our latest results, and discuss some of their implications for our
understanding of the formation and evolution of planetary systemsin star clusters, the angular momentum evolution of Sun-like stars, and for developing a new technique to determine stellar ages - gyrochronology.
- Host: Professor Robert Mathieu
- Careers for Physicists
- What can you do with a degree in physics?
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Dr. Johannes Loschnigg
- Abstract: Dr. Loschnigg was a Senior Policy Analyst at the White House Office of Science and Technology Policy (OSTP) in Washington DC from 2009 to 2013. As a member of OSTP's Environment and Energy Division, he was responsible for the development of federal policy for renewable energy, climate change, aerospace, and earth satellite observations. Prior to that, Dr. Loschnigg was the Staff Director for the Subcommittee on Space and Aeronautics of the Committee on Science in the U.S. House of Representatives, overseeing NASA and U.S. civil space programs. Dr. Loschnigg first came to the U.S. Congress in 2002 as a congressional science and technology policy fellow for the American Association for the Advancement of Science (AAAS), working for U.S. Senator Joseph Lieberman of Connecticut. While in the Senate he directed the development of legislation relating to innovation, broadband wireless communication, nanotechnology, defense research, and climate change policy. Between 1998 and 2002, Dr. Loschnigg was affiliated with the University of Hawaii, initially as post-doctoral fellow and later as a faculty research scientist in atmospheric and oceanic sciences, where he concentrated on coupled ocean-atmosphere modeling and impacts of climate variability on disease and human health. <br><br><br>
Dr. Loschnigg has also been a Senior Advisor for the Administrator at NASA Headquarters in Washington DC, consultant for the National Academy of Sciences, scientific assistant at the NASA Ames Research Center in California and the Department of Physics at the University of Freiburg in Germany. Dr. Loschnigg holds BA degrees in both physics and international relations from the University of Wisconsin-Madison, and MS and PhD degrees in astrophysical, planetary and atmospheric sciences from the University of Colorado at Boulder. He currently is a consultant providing strategic advice for organizations and companies in areas such as energy, aerospace, and climate change.
- Host: McCammon
- Graduate Introductory Seminar
- Condensed Matter Physics
- Time: 4:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Coppersmith, Eriksson, Joynt, Levchenko, McDermott, Onellion, Rzchowski, Vavilov, Winokur