In the second part of this talk I will speculate on how thermalization in heavy-ion collisions is achieved in the first place. I will demonstrate that the time-dependent quantum fluctuations can drive a system of coherent classical fields to evolve in accordance with ideal hydrodynamics. Evidence for these quantum fluctuations in the proton has recently been seen at the LHC with the recent announcement by the CMS collaboration of a long range rapidity correlation in proton-proton collisions.
To some extent, SWNT liquids were (and still are) considered an oxymoron because dispersing or dissolving SWNTs into fluid phases proved exceedingly difficult. From the fundamental physics viewpoint, SWNT fluids should be complex, because of the presence of intermediate length scales between those of the solvent molecules and those of a macroscopic flow.
In this lecture, I will discuss how SWNTs can and should be viewed as hybrids between polymer molecules and colloidal particles. Even at low concentrations (few parts per million), SWNTs form complex fluid phases with intriguing properties. When stabilized properly, dilute SWNTs behave as Brownian rods. Indeed, we show that they are the best model system for studying the dynamics of stiff filaments, an important area of polymer physics and biophysics. By using SWNTs, we resolve a three-decade old controversy on the Brownian diffusion of slender rods in crowded environments. We also show that, when the solvent is appropriate and the concentration sufficiently high, SWNTs self-assemble into novel liquid crystalline phases. Understanding these phases requires extending classical theories to include the effects of short-range repulsion and long-range attraction between rods. We show that SWNT liquid crystals have great potential application in the manufacturing of well-aligned SWNT fibers.
Measured atom distribution on a lattice for a BEC (left) and Mott insulators (middle & right). Each point
marks the detected position of a single atom.
In this talk I will focus on the physics of devices based on the bulk heterojunction approach, which relies on a nanoscale blend of electron-donating and electron-accepting molecules. These solution-processed devices can be made relatively inexpensively and rapidly. But there is a price to be paid: the active layer materials are intrinsically disordered in their morphology and heterogeneous in their optical and electronic structure. Understanding the correspondence between the disordered molecular structure and the resulting mesoscopic device properties such as charge carrier density, electric field distribution, etc. will be essential if device efficiencies are to approach thermodynamic limits. I will discuss a variety of experiments and simulations being undertaken by my group and collaborators aimed at understanding the morphological and energetic landscape of the blend. These include time-resolved photoluminescence and carrier transport measurements that reveal the disordered nature of the materials and also impedance spectroscopy measurements that show the presence of intrinsic, defect-induced carriers that lead to Schottky behavior at the electrodes. I will also discuss the origin of the open-circuit-voltage of the device and how it is impacted by ground state interactions. Lastly, I will discuss some more "exotic," multiphoton mechanisms that are capable in principle of yielding higher device efficiencies.
Contact: Michael Hermele