225 research outputs found
Interference and Interaction in Multiwall Carbon Nanotubes
We report equilibrium electric resistance R and tunneling spectroscopy dI/dV
measurements obtained on single multiwall nanotubes contacted by four metallic
Au fingers from above. At low temperature quantum interference phenomena
dominate the magnetoresistance. The phase-coherence and elastic-scattering
lengths are deduced. Because the latter is of order of the circumference of the
nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV
spectrum which is in good agreement with the density-of-states (DOS) due to the
one-dimensional subbands expected for a perfect single-wall tube. As a function
of temperature T the resistance increases on decreasing T and saturates at
approx. 1-10 K for all measured nanotubes. R(T) cannot be related to the
energy-dependent DOS of graphene but is mainly caused by interaction and
interference effects. On a relatively small voltage scale of order 10 meV, a
pseudogap is observed in dI/dV which agrees with Luttinger-Liquid theories for
nanotubes. Because we have used quantum diffusion based on Fermi-Liquid as well
as Luttinger-Liquid theory in trying to understand our results, a large
fraction of this paper is devoted to a careful discussion of all our results.Comment: 14 pages (twocolumn), 8 figure
Fed-batch control based upon the measurement of intracellular NADH
A series of experiments demonstrating that on-line measurements of intracellular NADH by culture fluorescence can be used to monitor and control the fermentation process are described. A distinct advantage of intercellular NADH measurements over other monitoring techniques such as pH and dissolved oxygen is that it directly measures real time events occurring within the cell rather than changes in the environment. When coupled with other measurement parameters, it can provide a finer degree of sophistication in process control
Femtosecond data storage, processing and search using collective excitations of a macroscopic quantum state
An ultrafast paralell data processor is described in which amplitude mode
excitations of a charge density wave (CDW) are used to encode data on the
surface of a 1-T TaS_2 crystal. The data are written, manipulated and read
using parallel femtosecond laser pulse beams, and the operation of a database
search algorithm is demonstrated on a 2-element array.Comment: To be published in App. Phys. Let
Charge sensing in carbon nanotube quantum dots on microsecond timescales
We report fast, simultaneous charge sensing and transport measurements of
gate-defined carbon nanotube quantum dots. Aluminum radio frequency single
electron transistors (rf-SETs) capacitively coupled to the nanotube dot provide
single-electron charge sensing on microsecond timescales. Simultaneously, rf
reflectometry allows fast measurement of transport through the nanotube dot.
Charge stability diagrams for the nanotube dot in the Coulomb blockade regime
show extended Coulomb diamonds into the high-bias regime, as well as even-odd
filling effects, revealed in charge sensing data.Comment: 4 pages, 4 figure
Electronic properties of molecular solids: the peculiar case of solid Picene
Recently, a new organic superconductor, K-intercalated Picene with high
transition temperatures (up to 18\,K) has been discovered. We have
investigated the electronic properties of the undoped relative, solid picene,
using a combination of experimental and theoretical methods. Our results
provide detailed insight into the occuopied and unoccupied electronic states
Tunable Polaronic Conduction in Anatase TiO2
Oxygen vacancies created in anatase TiO2 by UV photons (80–130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission reveals that the quasiparticles are large polarons. These results indicate that anatase can be tuned from an insulator to a polaron gas to a weakly correlated metal as a function of doping and clarify the nature of conductivity in this material.open1192sciescopu
Ground state properties of a confined simple atom by C fullerene
We numerically study the ground state properties of endohedrally confined
hydrogen (H) or helium (He) atom by a molecule of C. Our study is based
on Diffusion Monte Carlo method. We calculate the effects of centered and small
off-centered H- or He-atom on the ground state properties of the systems and
describe the variation of ground state energies due to the C parameters
and the confined atomic nuclei positions. Finally, we calculate the electron
distributions in plane in a wide range of C parameters.Comment: 23 pages, 9 figures. To appear in J.Phys. B: Atom. Mol. Op
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