Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session R18: Focus Session: Carbon Nanotubes: Transport II |
Hide Abstracts |
Sponsoring Units: DMP Chair: Brian LeRoy, TU Delft Room: Baltimore Convention Center 315 |
Wednesday, March 15, 2006 2:30PM - 3:06PM |
R18.00001: Quantum Dephasing and Decoherence in Carbon Nanotubes : Role of Electron-Phonon coupling Invited Speaker: In this talk, the role of electron-phonon coupling on quantum transport is addressed in clean and disordered carbon nanotubes. Defects and impurities are modelled by static disorder, whereas dynamic disorder is driven by the time-dependent vibrations of carbon atoms, that impact on the electronic overlap matrix coupling. On the basis of the Kubo framework in the coherent regime, the conductance scaling properties in the weak localization regime are explored, and from the incorporation of the superimposed effect of acoustic phonon modes phonon, the energy-dependent coherence length and coherence times will be derived, following a phenomenological perspective. Additionally, the strong disturbance of the electronic structure due to optic modes is analyzed, and shown to strongly alter the conductance scaling behaviour of both metallic and semiconducting otherwise clean nanotubes. Consequences for the high-bias regime of nanotubes-based field effect transistors and limitations of semi-classical focus will be discussed. [Preview Abstract] |
Wednesday, March 15, 2006 3:06PM - 3:18PM |
R18.00002: Combined electrical transport and STM of carbon nanotubes B.J. LeRoy, I. Heller, V.K. Pahilwani, C. Dekker, S.G. Lemay We have performed simultaneous electrical transport and scanning tunneling spectroscopy measurements on suspended carbon nanotubes. By combining these two measurement techniques we are able to probe the electronic states involved in transport through the nanotube. The spectroscopy shows peaks due to Coulomb blockade, which split and change energy as a function of the source-drain voltage across the nanotube. These peaks track the Fermi level of the source and drain electrodes. Unexpectedly, the strength of the peaks also depends on position along the tube. [Preview Abstract] |
Wednesday, March 15, 2006 3:18PM - 3:30PM |
R18.00003: Role of electronic excitations in ion collisions with carbon nanostructures. David Tomanek, Yoshiyuki Miyamoto, Arkady Krasheninnikov We study the effect of electronic excitations during collisions of protons with $sp^2$ bonded carbon nanostructures by performing molecular dynamics simulations. To obtain microscopic insight into the collision process in real time, we combine time-dependent density functional calculations for electrons with molecular dynamics simulations for ions, and compare the results to molecular dynamics simulations in the electronic ground state. The simulations for protons colliding with carbon nanotubes and graphite are performed in the interesting range of impact energies of tens to hundreds of eV, corresponding to ion velocities covering a broad range around the Fermi velocity of the target, v$_F$=$8{\times}10^5$ m/s. In agreement with the binary collision approximation, we find only negligible deviations from Born-Oppenheimer dynamics for projectile velocities well below the Fermi velocity. Our results establish validity limits for the Born-Oppenheimer approximation, and also the threshold energy for sputtering of carbon nanotubes and graphite. [Preview Abstract] |
Wednesday, March 15, 2006 3:30PM - 3:42PM |
R18.00004: Electrical conducting and breakdown behaviors of multiwall carbon nanotubes under different contact modes Shuo Chen, J.Y. Huang, S.H. Jo, Z.Q. Wang, D.X. Han, G. Chen, M. Dresselhaus, Z.F. Ren We have carried out electrical transport property studies of individual multiwall carbon nanotubes while viewing the structural changes in-situ inside a high resolution transmission electron microscope. Two types of contact have been tested: end-contact with all layers contacted with the electrodes, and side-contact with only the outmost layer contacted with the electrodes. We found that in some cases electrical breakdown takes place in the innermost layer under both contact modes with a simultaneous current drop, which indicates that under high bias voltage, each layer carries a current even there is no direct contact with the electrodes. Eexperimental evidence shows that the temperature can reach around $3000\,^\circ$C during breakdown, so the inter-layer conducting could be induced by strong electric field or by thermal excitation. [Preview Abstract] |
Wednesday, March 15, 2006 3:42PM - 3:54PM |
R18.00005: Distinct properties of single-wall carbon nanotubes with sidewall chemical functionalization Jianping Lu, Hyoungki Park, Jijun Zhao \textit{Ab initio }calculations reveal distinct electronic properties associated with side wall functionalization of SWNTs. The metallic tubes are found to be more reactive than the semiconducting ones. The hybridization between the addend and the tube induces unique impurity states near the Fermi level. For semiconducting tubes the state is localized near the functionalized site with a characteristic length of 15 {\AA}. In contrast, the impurity state is extended and acts as a strong scattering centre in metallic tubes. This effect greatly hinders the ballistic transport of electrons along the metallic nanotubes. The characteristic dependence of the electronic states and the conductance on functional molecules provides possible pathways for chemical sensor applications and the band structure engineering. [Preview Abstract] |
Wednesday, March 15, 2006 3:54PM - 4:06PM |
R18.00006: Effects of sidewall functionalization on the conducting properties of SWNTs Hyoungki Park, Jijun Zhao, Jianping Lu We investigated the conducting properties of sidewall functionalized SWNTs with a finite addend concentration. Robust differences are found between monovalent and divalent addends. For monovalent addition a small number of addends can significant disrupt the ballistic conductance of nanotubes near the Fermi level. As the addend concentration increases the conductance rapidly decreases and approaches zero at addends to C ratio around 25{\%}. In contrast, divalent addends have only weak effects on the conducting properties and the nanotube quantum conductance remains above 1 even for addend concentration as large as 25{\%}. These differences can be attributed to the formation of impurity state near the Fermi level for monovalent addition, while divalent addends create impurity states far away from the Fermi level. [Preview Abstract] |
Wednesday, March 15, 2006 4:06PM - 4:18PM |
R18.00007: Theory of scanned-gate microscopy of carbon nanotubes and nanowires Matthew Zhang, Misha Fogler We model theoretically a scanned-gate microscopy experiment where a Coulomb-blockaded metallic carbon nanotube (nanowire) is probed by an AFM tip. The tip modifies the charge of the nanotube via an electrostatic coupling. The amount of induced charge can have a complicated dependence on the position and the voltage of the tip in a realistic experimental situation where several screening gates and nearby stray charges may be present, which may obscure the interpretation of the results. We demonstrate that such difficulties can be significantly reduced in the geometry where a nearby backgate screens the electrostatic interactions making them short-range. We show that it is then possible to calculate and simply distinguish among different contributions to the induced charge. Combining the above electrostatic modelling with many-body bosonization methods we demonstrate that the presence of the tip causes an oscillatory shift in the Coulomb blockade peak positions. We show that the amplitude and the phase of this shift can be used to study the spin-charge separation and Luttinger-liquid effects in one-dimensional wires. [Preview Abstract] |
Wednesday, March 15, 2006 4:18PM - 4:30PM |
R18.00008: Re-entrant semiconducting behavior of zigzag carbon nanotubes on substitutional doping by oxygen dimers Seung-Hoon Jhi The electronic structures of carbon nanotubes doped with oxygen dimers are studied using the {\it ab initio} pseudopotential density functional method. The fundamental energy gap of zigzag semiconducting nanotubes exhibits a strong dependence on both the concentration and configuration of oxygen dimer defects that substitute for carbon atoms in the tubes and on the tube chiral index. For a certain type of zigzag nanotube when doped with oxygen dimers, the energy gap is closed and the tube becomes semimetallic. At higher oxygen-dimer concentrations the gap reopens, and the tube exhibits semiconducting behavior again. The change of the band gap of the zigzag tube is understood in terms of their response to the strains caused by the dimer substitutional doping. [Preview Abstract] |
Wednesday, March 15, 2006 4:30PM - 4:42PM |
R18.00009: Modulated conduction in single-walled carbon nanotubes using covalently bound chromophore functionalities Jason Simmons, Tyler Mark, Guangde Chen, Victoria Campbell, Padma Gopalan, Mark Eriksson Carbon nanotube hybrid materials are widely studied in order to leverage the exceptional thermal and electronic properties for a number of applications. We demonstrate an optically active nanotube-hybrid material by covalently functionalizing single-walled nanotubes with an azo-based chromophore. Upon UV illumination, the conjugated chromophore functionality undergoes a cis-trans isomerization, breaking the conjugation and modulating the conductance of individual functionalized nanotubes. Though there is most likely no direct charge transfer between the chromophore and the nanotube, the isomerization results in a charge redistribution near the nanotube, modifying the local electrostatic environment and causing the change in conductance. Further, the conductance change is reversible; indicating that the chromophore functionalized nanotubes can be used as reversible photo-switches. [Preview Abstract] |
Wednesday, March 15, 2006 4:42PM - 4:54PM |
R18.00010: Electron Transport in Carbon Nanotubes with Superconducting Contacts Alexander Makarovski, Gleb Finkelstein We report on our measurements of electron conductance in single-walled carbon nanotubes contacted by superconducting leads. We study the proximity effect induced by the superconducting contacts at temperatures below the transition temperature of the leads. Excess differential conductance (way above the ballistic limit of $4e^2/h$ for a single-wall nanotube with normal contacts) and sub-gap Andreev reflection peaks are observed. [Preview Abstract] |
Wednesday, March 15, 2006 4:54PM - 5:06PM |
R18.00011: Superconductivity in entirely end-bonded multi-walled carbon nanotubes Junji Haruyama, Izumi Takesue, Naoki Kobayashi, Shohei Chiashi, Shigeo Maruyama, Toshiki Sugai, Hisanori Shinohara One-dimensional (1D) systems face some obstructions that may prevent the emergence of superconductivity(SC), e.g., 1.a Tomonaga-Luttinger liquid (TLL), 2.Peierls transition, and 3.Low density of states due to VHSs. A carbon nanotube (CN) is one of the best candidates for investigating a possibility of 1D SC and its interplay with such obstructions. Only two groups have experimentally reported SC in ropes of single-walled CNs (SWNTs) and very thin SWNTs [1] to date. In addition, those interplay with 1D phenomena have never been clarified. Some theoretical papers also predicted strong correlation between TLL states and SC for SWNT ropes and importance of electron-phonon interaction for thin SWNTs [2]. Here, we report that entirely end-bonded multi-walled CNs (MWNTs) can show SC with the T$_{c}$ as high as 12K [3] (about 50-times larger than T$_{c}$ in former of [1]). We find that emergence of this SC and its interplay with TLL states are highly sensitive to junction structures of Au electrode/MWNTs. Only MWNTs with optimal numbers of electrically activated shells realized by the entire end-bonding can allow the SC due to intershell effects. \textbf{Refs.} \textbf{1.}M. Kociak, et al., PRL 86, 2416 (2001); Z. K. Tang, et al., Science 292, 2462 (2001), \textbf{2}.J.Gonzalez, PRL 88, 076403 (2002); R.Barnett, et al., PRB 71, 035429 (2005), \textbf{3}.J.Haruyama et al., PRL Accepted [Preview Abstract] |
Wednesday, March 15, 2006 5:06PM - 5:18PM |
R18.00012: Zero-bias anomaly and possible superconductivity in single-walled carbon nanotubes Jian Zhang, Alexander Tselev, Yanfei Yang, Kyle Hatton, Paola Barbara, Serhii Shafraniuk We report measurements of field-effect transistors made of isolated single-walled carbon nanotubes contacted by superconducting electrodes. For large negative gate voltage, we find a dip in the low-bias differential resistance. Surprisingly, this dip persists well above the superconducting transition temperature of the electrodes, indicating that it is not caused by superconducting proximity effect from the electrodes. This conclusion is supported by measurements on carbon nanotubes contacted by normal electrodes showing similar features. One possible explanation is superconductivity in the nanotubes. [Preview Abstract] |
Wednesday, March 15, 2006 5:18PM - 5:30PM |
R18.00013: Shell filling and excited states in a fully tunable double quantum dot on a carbon nanotube Sami Sapmaz, Carola Meyer, Piotr Beliczynski, Pablo Jarillo-Herrero, Leo Kouwenhoven We have realized fully controllable and tunable nanotube quantum dots defined with electrostatic top-gates. Using three electrostatic top-gates we have made a NT double dot. Clear honeycomb patterns are observed in the charge stability diagram as a function of two independent side-gates. Furthermore, for the first time we have observed discrete excitations at finite bias. The origin of these excitations is discussed. The central top-gate is used to control the coupling between the two NT dots. Controlling electron interactions in a molecular system is important for many applications such as for example quantum computation. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700