Physics

Seminars in Fall 2014

All seminars are held at 4:10 PM in Bio 19, unless otherwise noted.
Refreshments will be served at 4:00 PM.

Upcoming Seminar

September 3, 2014

Thesis Start-Up Meeting

Sept 3

Thesis Start-Up Meeting

Sept 10

Summer Internship Talks

Sept 17

Summer Internship Talks

Sept 24

Spencer Chang, University of Oregon

Oct 1

Andrew Essin, Caltech

Exotic Quantum Numbers in Exotic Phases of Matter

Symmetries imply conservation laws and therefore provide meaningful and useful ways to label and classify states of particles and matter. Condensed matter physics traditionally classifies phases of matter by patterns of symmetry breaking.  One of the most exciting areas of current research is the study of phases which break no symmetries, because the distinctions between them cannot be captured within the traditional scheme.  I will focus on exotic phases of matter that are host to "fractional excitations," and will describe how fractional excitations can carry "fractional quantum numbers." 
Oct 8

Summer Internship Talks/CAT Presentation

Oct 15

Matthew Graham, Oregon State University

Micro-Femto Energetics; Nano-Physics in the Twinkling of an Eye

When light and matter interact, electron micro-femto energetics begin.  Our just-constructed lab is able ‘film’ the excited electron’s energetic journey from light absorption to photocurrent generation with sub-micron (<10-6 m) spatial resolution and femtosecond (~10-15 s) time-resolution.  By 'filming' how electrons move and relax at nanoscale interfaces, we identify the bottlenecks that inherently limit the efficiency of solar voltaics and photosensors.  We will show how our ultrafast ‘moives’ give a time-space resolved microscopy map of the electronic population in materials such as graphene and single atomic layer dichalcogenides devices.  For graphene, our measurements reveal how electrons relax near the Fermi energy through a radically accelerated supercollision mechanism. The discovery of this novel electronic mechanism provides the missing link required to predict current generation from electronic population in graphene.

Oct 22

Fall Break

Oct 29

Ian Coddington, National Institute of Standards and Technology, Boulder

Nov 5

Robert Knapp, Evergreen College

Nov 12

Anne Trehu, Oregon State University

Nov 19

Ben McMorran, University of Oregon

Experiments with Free Electron Vortices

Electron vortex beams are composed of free electrons in quantized orbital states. Each electron wave packet in the beam has a helical shape, with a resulting quantized orbital angular momentum (OAM) and a corresponding magnetic moment. To produce such states, we use nanofabricated diffraction gratings to holographically “sculpt” a phase vortex onto free electron matter waves in a transmission electron microscope (TEM). We also use this approach to place free electrons in coherent superpositions of orbital states. These beams can interact with surfaces and materials in unique, albeit subtle, ways. For example, electron vortex beams can transfer quantized OAM to another system through inelastic scattering. In the TEM this can result in OAM-dependent signals and images that can provide new magnetic, plasmonic, and structural information about a material. These applications, the new technologies developed to achieve them, and the fundamental physics of free electron orbital states will be discussed.

Nov 26

Thanksgiving Break

Dec 3

Thesis Talk

Dec 10

Max Schlosshauer, University of Portland

A New "No-Go" Result for Quantum Mechanics

I describe a new theorem that shows that whenever you consider a pair of quantum systems, the whole is different from the sum of the parts even in the absence of entanglement. (Reference: Phys. Rev. Lett. 112, 070407 (2014), arXiv:1306.5805 [quant-ph])