Events at Physics |
Events on Thursday, October 8th, 2009
- R. G. Herb Condensed Matter Seminar
- Transport properties of superconductors near critical temperature: conductivity, magneto-tunneling, noise and relaxation
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Alex Levchenko, Argonne National Lab
- Abstract: We study fluctuation effects on transport properties of superconductors (thin films and tunnel junctions) above the transition temperature. The exact frequency dependence of the electron phase relaxation time due to dynamical superconducting fluctuations is important in this regime. It strongly modifies temperature and magnetic field dependence of conductivity, tunneling conductance and noise. A new energy scale appears as the result of these fluctuation effects, which provides a natural reqularization to Maki-Thompson conductivity and leads to peculiar non-monotonous temperature dependence of tunneling conductance. We make a comparative analysis of diffusive and ballistic regimes in the context of tunneling and go beyond the standard paradigm of density of states related effects. Noise measurement may be a powerful tool for probing superconductive fluctuations, since spectral function of current fluctuations exhibits a distinct feature at the Josephson frequency and its magnitude is strong function of temperature.
- Host: Maxim Vavilov
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Parity violation in low energy NN interactions
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Roxanne Springer, Duke University
- Abstract: At low energies, parity violation in NN scattering
(including photons) is described by an effective field theory (EFT)
that includes only contact interactions. I will describe this EFT,
how it improves upon the standard (non-physical) description, how it
echoes the Danilov treatment, and how its predictions compare to
existing (presently under-constraining) measurements. - Host: Michael Ramsey-Musolf
- Introductory Graduate Seminar
- Nuclear Experimental/Theory
- Time: 5:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Balantekin, Heeger, Knutson, Ramsey-Musolf, University of Wisconsin Department of Physics