Transport in Nanotubes and Nanostructures
Tsuneya Ando, Hidekatsu Suzuura
Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
The purpose of this talk is to give a brief review on recent theoretical investigations on transport properties of carbon nanotubes. The topics include an effective-mass description of electronic states, absence of backward scattering except for scatterers with a potential range smaller than the lattice constant and some examples of related experiments, a conductance quantization in the presence of short-range and strong scatterers such as lattice vacancies, phonons and electron-phonon scattering, contacts with a metallic electrode, and junctions and topological defects.
Transport in disordered multiwalled carbon nanotubes
Reeta Tarkiainen, Markus Ahlskog, Pertti Hakonen, Mikko Paalanen
Low Temperature Laboratory, P.O.Box 2200, FIN-02015 Helsinki University of Technology, Finland
We have studied electric transport in CVD synthesized multiwalled carbon nanotubes (MWNT), with contact resistances around 5 kW. Contrary to arc-discharge grown MWNTs that are close to ballistic, these tubes are rather resistive, 30-100 kW/mm. At low temperatures (T < 30 K), a zero-bias anomaly of tunneling into diffusive 1D wire appears, which behaves differently from that reported for MWNTs grown in arc-discharge: our data does not collapse into a universal curve in a G(V)/Ta vs. ln(V/T) plot. A tunnel junction with RC transmission line environment looks like the most suitable model. Indeed, at large bias the first order correction to conductance is proportional to 1/ÖV. Recent theoretical treatment gives similar results (Rollbühler et al., Phys. Rev. Lett. 87, 2001), G(V) µ exp(-Ö{V/V0}), even though our experiment does not conform to the weak tunneling assumption of the calculation.
Tunneling into 1D and Quasi-1D Conductors: Luttinger-Liquid Behavior and Effects of Environment
Edouard Sonin
Racah Institute of Physics, Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel
The paper addresses the problem whether and how is it possible to detect the Luttinger-liquid behavior from the IV curves for tunneling to 1D or quasi-1D conductors. The power-law non-ohmic IV curve, which is usually considered as a manifestation of the Luttinger-liquid behavior in nanotubes, can be also deduced from the theory of the Coulomb blockaded junction between 3D conductors affected by the environment effect. In both approaches the power-law exponents are determined by the ratio of the impedance of an effective electric circuit to the quantum resistance. Though two approaches predict different power-law exponents (because of a different choice of effective circuits), the difference becomes negligible for a large number of conductance channels.
Anomalous Negative Magnetoresistance of Multi-Walled Carbon Nanotube with Ni78Fe22 Electrodes
Jinhee Kima, Jae-Ryoung Kimb, Jong Wan Parkb, Ju-Jin Kimb, Nam Kima, Byung Chill Wooa
aElectronic Device Group, Korea Research Institute of Standards and Science, Daejeon 305-600, Korea
bDepartment of Physics, Chonbuk National University, Jeonju 561-756, Korea
We have investigated the electrical transport properties of a multi-walled carbon nanotube with ferromagnetic Ni78Fe22 electrodes at low temperatures. Magnetoresistance curve was non-hysteretic and exhibited a pronounced dip structure at the external field of 160 Oe. Magnetoresistance ratio depended on bias current and became as high as 35% at low bias current. Two- and four-probe measurements gave similar results. Such anomalous features in the magnetoresistance curve persisted up to 10 K.
Driving current through single organic molecules
H. B. Webera, J. Reicherta, R. Ochsa, D. Beckmanna, M. Mayora, H. v. Löhneysenb
aForschungszentrum Karlsruhe, Institut for Nanotechnology, D-76021 Karlsruhe
bForschungszentrum Karlsruhe, Institut for Solid State Physics, D-76021 Karlsruhe, and Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe
We have performed conductance measurements with a gold-molecule-gold junction employing the mechanically controlled break junction technique. The organic sample molecules form a stable chemical bridge between the electrodes. Two molecules, which differ essentially by their spatial symmetry, showed discrete stable conductance patterns (IVs), which reflect the symmetry/asymmetry of the sample molecules. This allows to identify the IVs as transport through our sample molecules. The observed sample-to-sample fluctuations demonstrate the strong influence of microscopic details. The body of our data strongly suggests that each stable IV is related to current through only one single molecule.