- Joseph W. Lauher
Department of Chemistry
Crystals by Design
| The idea is a simple one. Identify some supramolecular goal. Design a molecule or molecules that would self-assemble to yield your desired structure. Go into the lab and synthesize the required compounds, grow a single crystal and use X-rays to determine the structure. Can this be done? Sometimes it can, if you are lucky and have a good day. Of course a good design and some skilled students in the lab can help you on your way. The picture shows two superimposed crystal structures obtained at different times from the same crystal. In the background is a array of diacetylene monomers. In the foreground the corresponding polymer as obtained from a subsequent single crystal-to-single crystal topochemical polymerization is shown. This supramolecular structure was designed, synthesized and characterized by Stony Brook graduate student Mr. Zhong Li. |
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- Emilio Mendez
Department of Physics and Astronomy
When the Noise is the Signal in Semiconductor Heterostructures
Host: Allen
- Girsh Blumberg
Bell Labs
Competing orders in low-dimensional doped quantum spin systems
For doped two-dimensional quantum spin systems the competition between insulating states at low carriers concentration and superconductive pairing at higher densities has emerged as a key feature of the high-Tc problem. We study magnetic correlations in low- dimensional quantum systems and the carrier dynamics in doped antiferromagnetic environment with relevance to the phase diagram high-Tc cuprates. Magnetic correlations which give rise to a finite spin gap were predicted to generate an attractive interaction between doped carriers leading to superconductivity with a d-wave like order parameter. Novel ground states with broken translational symmetry in which single holes or hole pairs order in a crystalline pattern were observed. Refs: GB et al., Science 297 584 (2002); PRL91 087401 (2003); Nature 431 1078 (2004); PRL93 027001 (2004); PRL97 016403 (2006); PRL88 107002 (2002); etc.
Host: Abanov
- Eva Zurek
Max Planck Institut für Festkörperforschung, Stuttgart, Germany
DFT Studies of the 13C NMR Chemical Shifts of Single-Walled Carbon Nanotubes (SWNTs), Magic Metal-(C60)2 Clusters and NMTO Wannier-like Functions for Solids
DFT has been used to calculate the electronic structure and 13C NMR chemical shifts of finite (9,0) and infinte (n, 0) SWNTs with n ranging from 7 to 17. It is shown that direct comparison of the molecular and periodic approaches can be made if benzene is used as the internal (computational) reference. The results indicate that capping may have a strong effect on the computed properties. For the infinite systems, the shifts decrease roughly inversely proportional to the tube’s diameter. 13C NMR has the potential for becoming a useful tool in characterizing SWNT samples. The enhanced stability of so-called magic clusters is often explained by the formation of filled geometrical or electronic shells. Recent experiments on K- and Ba-C60 clusters have measured a set of magic peaks, which cannot be explained by either one of these mechanisms. We present DFT studies addressing the bonding and stability in Mn(C60)2 clusters, with M = K, Ba and 1 <= n <= 6. The importance of calculating entropy in the determination of the most stable configuration is discussed. A method that is able to generate truly minimal basis sets that accurately describe either a group of bands, a band or even just the occupied part of a band is outlined. These basis sets are the so-called NMTOs, muffin-tin orbitals of order N. The NMTOs are atom-centered and localized by construction, yielding Wannier functions for isolated bands. For bands that overlap others, Wannier-like functions may be generated. We show that NMTOs are able to give a chemical understanding of bonding within the solid state by applications to various systems.
Host: Allen
- Andrew Jordan
University of Rochester
Detectors - Eyes and hands to the microworld
All direct knowledge of the microworld comes to us through detectors. The basic physical principles underlying how measurement occurs will be introduced, as well as specific examples of detectors used in the laboratory. Focusing on quantum detectors, as well as detectors of statistical current fluctuations in mesoscopic conductors, I will highlight recent theoretical advances closely connected with parallel experimental activity.
Host: Averin
- Dima Averin
Stony Brook
Anyons in FQHE structures: edge-state tunneling, antidot transport, and quantum computation
Host: Allen
- Vasili Semenov
Department of Physics and Astronomy, Stony Brook University
Scylla of physical qubits and Charybdis of quantum computing: The new pass between
Host: Averin
- Elaine DiMasi
National Synchrotron Light Source Dept., Brookhaven National Laboratory
In-situ x-ray scattering studies of biomimetic mineralization
Host: Stephens
- Sanjay Sampath
Dept. Materials Science and Center for Thermal Spray Research
Thermal plasma spray: A Tool for Materials Synthesis from Extreme Conditions
This talk will be an overview thermal plasma spray technology as a tool for material synthesis and processing. Thermal plasmas are used widely in industry for a variety of coating applications. This presentation will discuss the technology in the context of collaborative work we did with (a) impact-based transformations (together with Stony Brook Geological Sciences), (b) rapid quenching effects, (c) synthesis of nanopowders, with applications in superconductivity, and (d) applications in precursor-based synthesis of functional nanomaterials. See also here. Host: Allen
- Nikolai Zhitenev
Bell Labs., Lucent Technologies
Electronic conducting states in nano- and mesoscale molecular junctions
Organic materials can offer new electronic functionality not available in the inorganic devices. However, the integration of organics within nanoscale electronic circuitry poses new challenges for material physics, chemistry and nanofabrication. I will discuss three approaches that we use to build small molecular devices. The first group of experiments is targeted toward wiring of a single or just a few molecules. Two other techniques screen the properties of larger molecular junctions with characteristic size of ~50-300 nm but instead allow for systematic experimenting with the topography, the chemical bonding at metal-molecule interface and the defect generation. Surprisingly, the results of all experiments show that the tunneling conductance of common short molecules is 4-6 orders of magnitude smaller than is commonly believed. Finally, I present a new molecular system based on monolayer of polymer macromolecules. There, the molecular states determining the transport properties can be controllably created and chemically modified. Host: Likharev
- Konstantin Arutyunov
University of Jyväskylä, Department of Physics, NanoScience Centre, Jyväskylä, Finland
Quantum fluctuations in ultranarrow superconducting nanowires
Abstract
Host: Averin
- Joel S. Miller
Department of Chemistry, University of Utah, Salt Lake City
Molecule-based Magnets: New Materials for this Millennium
Abstract
Host: Stephens
- Aleksey M. Tikhonov,
Center for Advanced Radiation Sources at the University of Chicago, and Brookhaven National Laboratory, National Synchrotron Light Source, Beamline X19C, Upton, NY, 11973, USA
X-ray Study of the Electric Double Layer at the Surface of Silica Hydrosol
According to my x-ray scattering data, the forces of electrical imaging strongly polarize the surface of colloidal silica solution. The transition region at both the air/hydrosol and the n-hexane/ hydrosol interfaces consist of three parts, i.e., a ~2-nm-thick compact layer of alkali ions, a loose monolayer of nanocolloidal particles as part of a thick diffuse layer, and a low-density layer sandwiched between them. Its structure is described by a model in which the potential gradient at the interface reflects the difference in the potentials of "image forces" for the cationic alkali ions and anionic nanoparticles and the specific adsorption of surface charge. In this presentation, I will discuss the density of water in the large electric field (~109-1011 V/m) of the transition region, the surface charge density, the in-plane structure of the compact layer and the value of surface tension at the sol's surface. In addition, I will discuss the difference in the adsorption of Cs+ and Na+ ions at the hydrosol's surface, which can be explained by the ion- size-dependent term in the electrostatic Gibbs energy equation derived earlier by others.
Host: Abanov