Torsional electromechanical quantum oscillations in carbon nanotubes (original) (raw)
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Origin of torsion-induced conductance oscillations in carbon nanotubes
Physical Review B, 2008
We combine electromechanical measurements with ab initio density-functional calculations to settle the controversy about the origin of torsion-induced conductance oscillations in multiwall carbon nanotubes. Contrary to intuition, the observed oscillation period in multiwall tubes exhibits the same inverse-squared diameter dependence as in single-wall tubes with the same diameter. This finding suggests an intrawall origin of the oscillations and an effective electronic decoupling of the walls, which we confirm in calculations of multiwall nanotubes subject to differential torsion. We exclude the alternative origin of the conductance oscillations due to changes in the interwall registry, which would result in a different diameter dependence of the oscillation period.
Diameter-dependent conductance oscillations in carbon nanotubes upon torsion
arXiv: Materials Science, 2008
We combine electromechanical measurements with {\em ab initio} density functional calculations to settle the controversy about the origin of torsion-induced conductance oscillations in multi-wall carbon nanotubes. According to our observations, the oscillation period is inversely proportional to the squared diameter of the nanotube, as expected for a single-wall nanotube of the same diameter. This is supported by our theoretical finding that differential torsion effectively decouples the walls of a multi-wall nanotube near the Fermi level and moves the Fermi momentum across quantization lines. We exclude the alternative explanation linked to registry changes between the walls, since it would cause a different diameter dependence of the oscillation period.
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Nanoelectromechanical systems (NEMs) hold promise for a number of scientific and technological applications. In particular, NEMs oscillators have been proposed for use in ultrasensitive mass detection, radio-frequency signal processing, and as a model system for exploring quantum phenomena in macroscopic systems. Perhaps the ultimate material for these applications is a carbon nanotube. They are the stiffest material known, have low density, ultrasmall cross-sections and can be defect-free. Equally important, a nanotube can act as a transistor and thus may be able to sense its own motion. In spite of this great promise, a room-temperature, self-detecting nanotube oscillator has not been realized, although some progress has been made. Here we report the electrical actuation and detection of the guitar-string-like oscillation modes of doubly clamped nanotube oscillators. We show that the resonance frequency can be widely tuned and that the devices can be used to transduce very small forces.
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Carbon nanotubes are one of the most important nanomaterials today. It exhibits an exceptional combination of physical, electrical, mechanical, and chemical properties, which results in their great potential of industrial application in various fields. Carbon nanotubes can be categorized as single-walled carbon nanotubes and multiwalled carbon nanotubes. The structure of a single-walled carbon nanotube can be viewed as one-atom-thick layer of graphite rolled cylinder. Well understanding the property of single-walled carbon nanotubes is fundamental in both exploratory research and the potential applications for Carbon nanotubes based products. These molecules also have a unique structure that encapsulates a one-dimensional volume of space. Electromechanical properties of Carbon nanotubes like piezoresistance and chirality of carbon atom make them roughly five times stronger than steel and five times more resistive than silicon. These properties substantiate the applicational array of...
Mechanical and electromechanical coupling in carbon nanotube distortions
Physical Review B, 2003
A simple approach is presented for using bond-stretching and bond-bending modes to describe the static deformations of carbon nanotubes and related actuation effects. This approach allows us to analyze various phenomena in a unified way and to clarify their relationships. We discuss gap energy modulation by external strains, dimensional and torsional deformations caused by charge injection, and stretch-induced torsion. We show how symmetry determines the property dependence on the chiral angle of nanotubes. Electrically driven actuator responses related to deformation-induced modulation of electron kinetic energy are particularly interesting and relevant for applications. The strong oscillatory dependence of these responses on the nanotube geometry is explained within an intuitively clear picture of bonding patterns. We show how anisotropic ͑shear͒ deformations play an important role in nanotubes, making their responses distinctly different from graphite's.
New Journal of Physics, 2010
We have theoretically investigated the electromechanical properties of a freely suspended carbon nanotube that is connected to a constant-current source and subjected to an external magnetic field. We show that self-excitation of mechanical vibrations of the nanotube can occur if the magnetic field H exceeds a dissipation-dependent critical value Hc, which we find to be of the order of 10-100 mT for realistic parameters. The instability develops into a stationary regime characterized by time periodic oscillations in the fundamental bending mode amplitude. We find that for nanotubes with large quality factors and a magnetic-field strength just above Hc the frequency of the stationary vibrations is very close to the eigenfrequency of the fundamental mode. We also demonstrate that the magnetic field dependence of the time averaged voltage drop across the nanotube has a singularity at H = Hc. We discuss the possibility of using this phenomenon for the detection of nanotube vibrations.
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Sensors and Actuators A-physical, 2007
Sensors are key components in an overwhelming wealth of systems for industrial and consumer applications. Further system miniaturization will demand for continuous down-scaling of sensor functions in such systems most likely towards nanoscale. Then new sensor device concepts will emerge to improve performance, e.g. sensitivity, or to utilize unique functional properties of nanoscale structures. This paper presents concepts and demonstrators
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Physical Review Letters, 2002
We report on the characterization of torsional oscillators which use multi-walled carbon nanotubes as the spring elements. Through atomic-force-microscope force-distance measurements we are able to apply torsional strains to the nanotubes and measure their torsional spring constants and effective shear moduli. We find that the effective shear moduli cover a broad range, with the largest values near the theoretically predicted value. The data also suggest that the nanotubes are stiffened by repeated flexing.