PHY 676 Solid State Seminar

Schedule for Fall, 1999

All talks are in Room B-131, except when otherwise noted. Regular seminar time is Friday 1:30PM. Here are links to the schedule for Spring, 1997 Fall, 1997, Spring, 1998 Fall, 1998 and Spring, 1999 . Condensed Matter faculty are welcome to add speakers to the list.

• Friday September 10, 1:30 PM
  A. Palevski
  (Tel Aviv University)
  "Current Distribution in Quantum Hall Effect"
  
  
• Friday September 17, 1:30 PM
  Robert Grober
  (Yale University)
  Spectroscopic imaging of quantum dots, free excitons and electron hole plasmas in a narrow GaAs quantum well
  This talk describes the spectroscopic imaging of a 2.8 nm GaAs/AlGaAs quantum well using solid immersion lens microscopy. This solid immersion lens technique achieves 250 nm spatial resolution with unity transmission efficiency. Photoluminescence studies yield images of the well known sharp-line emission indicative of naturally occurring quantum dots, allowing us to document the density and distribution of dots in the sample. Photoluminescence excitation spectroscopy shows evidence for the presence of a two-dimensional excitonic state which persists throughout the entire sample. We have verified this identification by directly imaging the diffusion of these free excitons. Finally, at high pump intensities we observe that these excitonic systems evolve into electron-hole plasmas. The plasmas originate in the dots and expand with increasing pump intensity, eventually spreading throughout the sample.
  
  
  
• Friday Sept. 24, 1:30 PM
  Christian Bernhard
  (Max-Planck-Institut, Stuttgart)
  Far-infrared ellipsometry using a synchrotron light source: The c-axis dielectric response of Y_1-xCa_xBa₂Cu₃O_7-d single crystals
  
  
• Friday October 1, 1:30 PM
  Yuval Oreg
  (Harvard University)
  Spin configurations and electron correlations in mesoscopic systems
  
  
• Friday October 8, 1:30 PM
  Dan Ralph
  (Cornell University)
  Torques and Tunneling in Nanomagnets
  When the size scale of electronic devices is shrunk to nanometer dimensions, new properties often emerge that are of value for technological applications or scientific research. I will discuss two examples from recent work on ferromagnetic devices. First, we have demonstrated a new mechanism by which applied currents can switch the direction of magnetic moments in a device, for instance to manipulate magnetic memory elements. Unlike traditional schemes which utilize a magnetic field to reorient moments, the new mechanism is due to a torque that results when a spin-polarized current scatters from a magnetic layer. Another property that emerges only in devices containing metal particles smaller than 10 nm in diameter is that electrons can be made to flow only via "electron-in-a-box" quantum states that are individually resolvable by means of tunneling measurements. I will discuss how the electronic energy level spectra in magnetic particles are different than in non-magnetic particles.
  
  
• Friday, October 22, 1:30 PM
  Ismail Karakurt
  (Case Western Reserve)
  "Weak localization of electrons on liquid helium surface"
  
  
• Friday, October 29, 1:30 PM
  Jukka Pekola
  (Jyvaskyla University, Finland)
  "TBA"
  
  
• Friday November 5, 1:30 PM
  Andras Janossy
  (Technical University, Budapest)
  "Magnetic resonance on fullerenes"
  
  
  Friday November 12, 1:30 PM
  John Bruno
  (ARL)
  "Interband cascade lasers"
  
  
• Friday November 19, 1:30 PM
  Peter D. Johnson
  (BNL)
  "High Resolution Photoemission Spectroscopy Studies of Low-Dimensional Oxides"
  
  
• Friday December 10, 1:30 PM
  Sergey Maslov
  (Dept. Physics, BNL)
  "Infrared conductivity of ultrathin Pb films: effects of granularity vs. localization"