The Kavli Symposia in Nanoscience 2010
The Kavli Symposium in Nanoscience was held September 6, 2010 at The Norwegian Academy of Science and Letters, Oslo
Light, Metal and Molecules
Surface plasmons have generated considerable interest in recent years for their potential applications from sensing to photonic devices. In this regard, subwavelength holes in optically thick metal films which give rise to resonant transmission due to the involvement of surface plasmons offer many interesting possibilities . Here we will focus on the exploration of surface plasmon -- molecule interactions in hole arrays and in single apertures. Results show that such aperture structures can, among other things, give rise to enhanced absorption, enhanced emission, strong coupling and index switching (e.g. ref. 2-4). Such results will be presented together with examples of ultra-fast caracterisation of the surface plasmon -- molecule hybdrid states. Finally, the implications for chemistry, from spectroscopy to modifying molecular state properties, will be discussed.
1. C. Genet and T.W. Ebbesen, Nature 445, 39 (2007). 2. J. Dintinger, S. Klein, F. Bustos, W.L. Barnes and T.W. Ebbesen, Phys. Rev. B 71, 035424 (2005). 3. J. Dintinger, I. Robel, P.V. Kamat, C. Genet and T.W. Ebbesen, Adv. Mat. 18, 1645 (2006). 4. A. Salomon, C. Genet and T.W. Ebbesen, Angew. Chem. Int. Ed. 48, 8748 (2009).
Artificial molecules built from colloidal nanocrystals
Colloidal nanocrystals can be thought of as artificial atoms, or units with controllable density of electronic states. In recent years we have been working on coupled colloidal nanocrystals, to create artificial molecules. One example involves branched nanocrystals, such as tetrapods, the individual branches of which can be wired up into a transistor. A more recent example involves the creation of regularly spaced colloidal quantum dots within a rod shaped semiconductor nanocrystal. In a third example, we can use DNA to direct the assembly of specific nanoparticle groupings. In all cases, we are able to observe strong coupling between individual nanocrystals, leading to collective behavior in the nanocrystal molecule. Such nanocrystal molecules may have significant applications in fields as diverse as biological imaging and renewable energy.
Graphene: Magic of Flat Carbon
Graphene -- a free-standing atomic plane of graphite -- is a wonder material. It has many superlatives to its name. It is the thinnest material in the universe and the strongest one ever measured. Its charge carriers exhibit the highest intrinsic mobility, have zero effective mass and can travel micron distances without scattering at room temperature. Graphene can sustain current densities million times higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation (rather than the standard Schrodinger equation), which allows the investigation of relativistic quantum phenomena in a bench-top experiment.
I will overview our work on graphene concentrating on its fascinating electronic and optical properties and speculate about future applications.
Interference between two indistinguishable electrons emanating from two independent sources
Very much like the ubiquitous quantum interference of a single particle with itself, quantum interference of two independent, but indistinguishable, particles is also possible. This interference is a direct result of quantum exchange statistics, however, it is observed only in the joint probability to find the two particles in two separate detectors. I will present an observation of interference fringes between two independent and non-interacting electrons in a two-electron interferometer. In the experiment, two independent and mutually incoherent electron beams, emanating from two separated sources, were each partitioned into two trajectories. The combined four trajectories enclosed an Aharonov-Bohm magnetic flux, while the two trajectories of a single electron did not enclose flux - hence, no single electron interference was possible. Consequently, individual currents and their fluctuations, in each of the four detectors, were found to be independent of the Aharonov-Bohm B flux - as expected. However, the cross-correlation between current fluctuations in two separate detectors exhibited strong Aharonov-Bohm interference oscillations. This observation is a direct signature of quantum entanglement between the spatial degrees of freedom of two electrons ("orbital entanglement") even though they never interacted with each other.
The Impact of Spintronics on the Information and Communication Technologies
Spintronics is mainly known for the Giant MagnetoResistance (GMR) and the considerable storage density increase brought by the application of the GMR to the read heads of hard discs. However the GMR was only the first step in the development of a new type of electronics which exploits the spin of the electrons and is now called spintronics. After a review of some of the recent advances, I will describe their expected impact on the computing and telecommunication technologies of tomorrow (and, more generally, on the "beyond CMOS" electronics).Wikipedia
Controlling Individual Spins in Semiconductors: Basic Physics and Applications to Quantum Information
This talk will summarize progress in recent years, by our group and others, to control and read the state of individual spins in quantum dots defined by electrostatic gates in semiconductor heterostructures, nanowires, and carbon nanotubes. For one or two spins, this "technology" is now in hand, and work is now underway toward integrating larger numbers of spins while maintaining full control over the system. Surprising fundamental discoveries have accompanied technical progress, particularly concerning interactions between electrons and nuclear spins in the host material. Open problems and yet-unaccomplished technical challenges will be emphasized in this presentation.