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<< April 2014 >>

Monday, April 7, 2014

Visualizing Topological Quantum States: From Dirac Edge States to Majorana Zero Modes.

Colloquium | April 7 | 4:15-5:30 p.m. | LeConte Hall, Room #1

Ali Yazdani, Professor of Physics, Princeton University

Department of Physics

Our understanding of phases of matter has moved beyond those defined in terms of broken symmetries, such as simple solids or magnets, to include phases characterized by topological order, such as the recently discovered topological insulators. These topological quantum phases, which are being realized in various materials or nanostructures, can harbor quasi-particle states that behave as Dirac,...   More >

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Monday, April 14, 2014

Physics with Antihydrogen Atoms

Colloquium | April 14 | 4:15-5:30 p.m. | LeConte Hall, Room #1

Joel Fajans, Professor of Physics, UC Berkeley

Department of Physics

Since trapping antihydrogen atoms, the ALPHA collaboration has begun to test fundamental symmetries with anti-atoms. In this talk I will present spectral measurements of an anti-atom (a test of CPT), a direct limit on matter-antimatter gravity with freefall type measurements (a test of the weak equivalence principle), and a precision charge neutrality test (a novel test of CPT.)

Monday, April 21, 2014

Sloppy Models, Differential Geometry, And How Science Works

Colloquium | April 21 | 4:15-5:30 p.m. | LeConte Hall, Room #1

Jamers Sethna, Professor of Physics, Cornell University

Department of Physics

Models of systems biology, climate change, ecosystems, and macroeconomics have parameters that are hard or impossible to measure directly. If we fit these unknown parameters, fiddling with them until they agree with past experiments, how much can we trust their predictions? We have found that predictions can be made despite huge uncertainties in the parameters -- many parameter combinations are...   More >

Monday, April 28, 2014

Slip Sliding Away: Atomic-scale Processes That Govern Friction And Wear

Colloquium | April 28 | 4:15-5:30 p.m. | LeConte Hall, Room #1

Robert Carpick, John Henry Towne Professor and Chair, University of Pennsylvania

Department of Physics

I will discuss recent atomic force microscopy studies of nanoscale single asperity contacts. First, the frictional behavior of truly 2-dimensional materials will be discussed. For contacts to graphene and other 2-D materials, friction depends strongly on the number of 2-D layers. An even stronger effect occurs when graphene is fluorinated, an effect which can be interpreted in the context of the...   More >