Events at Physics
Events on Friday, September 24th, 2010
- Condensed Matter Theory Group Lecture
- Weak chaos in the disordered nonlinear Schroedinger chain: destruction of Anderson localization by Arnold diffusion
- Time: 1:00 pm
- Place: 5310 Chamberlin
- Speaker: Denis Basko, Universite Joseph Fourier & CNRS, Grenoble, France
- Abstract: I will discuss the long-time equilibration dynamics of a strongly disordered one-dimensional chain of coupled weakly anharmonic classical oscillators, which is one of the simplest models allowing to study the effect of a classical nonlinearity on the Anderson localization. The system has chaotic behavior, and it is shown that chaos in this system has a very particular spatial structure: it can be viewed as a dilute gas of chaotic spots. Each chaotic spot corresponds to a stochastic pump which drives the Arnold diffusion of the oscillators surrounding it, thus leading to their relaxation and thermalization. The most important mechanism of relaxation at long distances is provided by random migration of the chaotic spots along the chain, which bears analogy with variable-range hopping of electrons in strongly disordered solids.
- Host: Maxim Vavilov
- Theory/Phenomenology Seminar
- Charmed Mesons -- Their Hadronic Decays and Mixing
- Time: 2:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Chiang-Wei Chiang, National Central University, Taiwan
- Host: Vernon Barger
- Physics Department Colloquium
- Bose Condensation, Superfluidity, and the Quantum Hall Effect
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Jim Eisenstein, Caltech
- Abstract: Composite particles consisting of an even number of fermions(e.g. 4He atoms) can pretend to be bosons. Bosons, of course, can Bose condense and do remarkable things. Superconductivity, which is certainly remarkable when you stop to think about it, result(sort of) from the Bose condensation of electron pairs. With this in mind, theorists have speculated since the early 1960s that excitons (electron-hole pairs in a semiconductor) might be able to do the same thing.
In this talk I will describe experiments done at Caltech on a special collection of excitons that exists in equilibrium and does indeed show many (but not all) of the expected signs of excitonic superfluidity. Surprisingly, the system in question is a double layer two dimensional electron gas. With no valence band holes in sight, where do the excitons come from?
- Host: Coppersmith