Asymmetry and nondispersivity in the aharonovbohm effect. Here, we have used the same technique, where we have succeeded to observe intrinsic magnetotransport behavior, to highlyaligned thin films with different type of carbon nanotubes, such as multi walled carbon nanotubes or swcnts with singlechirality. Our understanding of this effect is, however, based on the assumption that the electrons are strictly. The aharonovbohm effect, sometimes called the ehrenbergsidayaharonovbohm effect, is a quantum mechanical phenomenon in which an electrically charged particle is affected by an electromagnetic potential. We consider conductance due to the motion of electrons along the circumference of the tube as opposed to the motion parallel to its axis. We report the direct observation of spinsinglet dark excitons in individual singlewalled carbon. The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observations of the aharonovbohm effect at the nanoscale. Aharonovbohm interference and beating in singlewalled carbonnanotube interferometers jien cao, qian wang, marco rolandi, and hongjie dai department of chemistry and laboratory for advanced materials, stanford university, stanford, ca 94305, usa.
In doubly connected structures such as loops of wire threaded by a magnetic flux, the electrical conductance oscillates because of the aharonovbohm effect. In metallic nanotubes, in particular, the backward scattering is entirely suppressed for scatterers with. Theory of the aharonovbohm effect in carbon nanotubes. Author links open overlay panel jorg rollbuhler a arkadi. Our understanding of this effect is, however, based on the assumption that the electrons are. The values of x are found to be 14 mev for most nanotubes studied. Scanned probe microscopy of electronic transport in carbon nanotubes a.
We predict the key phenomenological features of this anomalous aharonovbohm effect in semiconductive and metallic tubes and the existence of a large metallic phase in the low flux regime of multiwalled nanotubes, also suggesting possible experiments to validate our results. In the two achiral zigzag and armchair systems the momentum lines are parallel to the edges of the brillouin zone or the. The exceptional lowdimensionality and symmetry of carbon. Aharonovbohm effect in normal metal quantum coherence and. Aharonovbohm oscillations in carbon nanotubes nature. In the following sections, we show how carbon nanotubes can be either. Shaping electron wave functions in a carbon nanotube with a. Focus 28, 4 in the aharonovbohm effect, proposed in 1959, quantum particles are affected in measurable ways by the classical electromagnetic potential, previously regarded as a purely mathematical construct.
It arises from the presence of a vector potential produced by an applied magnetic field. This phenomenon reflects the dependence of the phase of the electron wave on the magnetic field, known as the aharonovbohm effect, which causes a phase. The role of the vector potential is that of an intermediary which connects the quantum potential to the flux line in a localizable way. The appearance of the peak corresponds to the absence of backscattering in metallic. Aharonovbohm conductance modulation in ballistic carbon nanotubes. Optical signatures of the aharonovbohm phase in single.
The aharonovbohm effect, sometimes called the ehrenbergsidayaharonovbohm effect, is a quantum mechanical phenomenon in which an electrically charged particle is affected by an electromagnetic potential v, a, despite being confined to a region in which both the magnetic field b and electric field e are zero. Principle of operation and proof of concept john cumings,1, a. Conductivity in carbon nanotubes with aharonovbohm flux. The boltzmann conductivity is calculated for carbon nanotubes in the presence of an aharonovbohm magnetic ux. Here we report magnetoresistance mea surements on individual multiwalled nanotubes, which display pronounced resistance. Does it mean that it is a real observable in quantum mechanics. Over the century a hundred years for science, technology. Nano idea open access thermoelectric effect in an aharonovbohm ring with an embedded quantum dot jun zheng1, feng chi2, xiaodong lu2 and kaicheng zhang3 abstract thermoelectric effect is studied in an aharonovbohm interferometer with. Carbon nanotubes are novel quantum wires consisting of rolled graphite sheets. Further, the band gap of semiconducting tubes, or the energy difference between the peaks in the electronic density of. Anderson localization, conductance fluctuations, ab effect, edge state transport, quantum hall effect, the metal insulator transition effect, 1f electrical noise, the microwave terahertz radiation, bolometric effect and nanosensor devices. Magnetotransport studies of carbon based nano tubes by. The band gap drastically changes with a period of the.
Aharonov bohm effect of both metallic and semiconducting swcnt s 1. An effect that occurs in small disordered metallic conductors and causes conductance fluctuations in small nonsuperconducting rings and wires. Even in the presence of disorder, the quantum mechanical interference of electron wavefunctions can still be observed. Aharonovbohm ab effect which was predicted in 19591 and realized experimentally a year later. Aharonovbohm effect in carbon nanotubes hiroshi ajiki, tsuneya ando institute for solid state physics, university of tokyo, 7221 roppongi, minatoku, tokyo 106, japan abstract optical absorption spectra are calculated in carbon nanotubes in the presence of a magnetic flux parallel to the tube axis.
Excitons in carbon nanotubes with broken timereversal. Effects of strain or curvature manifest themselves as a prominent conductivity peak as a function of the ux. Aharonovbohm effect and plasma oscillations in superconducting tubes and rings e. The aharonovbohm effect shows that the local e and b. Aharonovbohm conductance modulation in ballistic carbon. Aharonovbohm interference and beating in singlewalled.
Magnetically induced field effect in carbon nanotube devices arxiv. Carbon nanotubes cnts are attracting tremendous interest as the object of fundamental studies in condensed matter and molecular physics as well as possible functional units for future nanodevices. The movie shows in realtime the gradual buildup of an interference pattern as we count electrons passing through an aharonovbohmring. Aharonovbohm effect and symmetry crossover in carbon. The aharonovbohm interference and beating in singlewalled. Theory of the aharonovbohm effect in carbon nanotubes tsuneya ando department of physics, tokyo institute of technology, 2121 ookayama, meguroku, tokyo 1528551, japan abstract. We study the interference of interacting electrons in toroidal singlewall carbon nanotubes coupled to metallic electrodes by tunnel junctions. Aharonovbohm effect is phenomenon which cant be describe in terms of classical mechanics and is of purely quantum origin. How could this be though, there is no force on the electrons. Semiconducting nanotubes are particularly promising for photonic device applications with their diameterdependent, direct band gaps, while metallic tubes are considered to be ideal candidates for a variety of electronic and electrical applications ranging from nanocircuit wires to power transmission cables. Aharonovbohm effects on optical phonons in carbon nanotubes kohta ishikawa and tsuneya ando department of physics, tokyo institute of technology,2121 ookayama, meguroku, tokyo 1528551, japan abstract. In fact there is no magnetic field anywhere the electrons are. By stokes theorem, the magnitude of the aharonovbohm effect can be calculated using the e and b. Magnetoresistance devices based on singlewalled carbon.
We study the interference of interacting electrons in toroidal singlewall carbon nanotubes coupled. The carbon tori and nanotubes, either pure or holedoped, are examined. Since only one electron can pass through the ring at a. On the other hand, the progress of various analytical techniques, including the electron microscope, supported by materials technology, has resulted in both scientific and. We show that singlewalled nanotubes represent the smallest cylinders exhibiting the aharonovbohm effect with rich interference and beating. Conductivity in carbon nanotubes with aharonovbohm flux takeshi nakanishi and tsuneya ando1 national institute of advanced industrial science and technology 1 umezono, tsukuba 3058568, japan and crest, jst 418 honmachi, kawaguchi, saitama 3320012 japan 1department of physics, tokyo institute of technology.
Chiral effects in normal and superconducting carbon nanotubebased nanostructures fizika nizkikh temperatur, 2010, v. Chiral effects in normal and superconducting carbon nanotubebased nanostructures. The dc conductance shows resonant features as a function of the gate voltage and the magnetic field. They are able to act as conducting molecular wires11,12,14,15,16,17,18, making them ideally suited for the investigation of quantum interference at the singlemolecule level caused by the. Some of the most striking features of cnts are related to the symmetry breaking effect of high magnetic fields threading the tube axis. We show that the peak separation is determined by the aharonovbohm phase due to the tubethreading magnetic. Also in carbon nanotubes cnts, the electronic wave function acquires an aharonovbohm phase.
Our understanding of this effect is, however, based on the assumption that the electrons are strictly confined on the tube surface, on trajectories that are not modified by curvature effects. We have observed fieldinduced optical anisotropy as well as red shifts and splittings of absorption and photoluminescence. Individual swnts can act as conducting wires 1,2, fieldeffect tran. This phenomenon reflects the dependence of the phase of the electron wave on the magnetic field, known as the aharonovbohm effect, which. The aharonovbohm effect, sometimes called the ehrenbergsidayaharonovbohm effect, is a quantum mechanical phenomenon in which an electrically charged particle is affected by an electromagnetic field e. Scanned probe microscopy of electronic transport in carbon. Aharonovbohm effects on conductivity in carbon nanotubes.
Aharonovbohm effect in carbon nanotubes sciencedirect. Chiral effects in normal and superconducting carbon. The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observation of the aharonovbohm effect at the nanoscale. Direct observation of dark excitons in individual carbon. Ab effect is, quite generally, a nonlocal effect in which a physical object travels along a closed loop through a gauge fieldfree region and thereby undergoes a physical change. Aharonovbohm effect from eric weissteins world of physics. Carbon nanotubes exhibit interesting transport properties. Optical absorption spectra for carbon nanotubes are calculated in the presence of an aharonovbohm flux passing through the cross section. Romanovsky, and uzi landman school of physics, georgia institute of technology, atlanta, georgia 303320430, usa. The aharonovbohm ab effect 1,2,3,4,5,6 entails the presence of a phase shift caused by a magnetic flux enclosed by an electron interferometer. What is the conclusion that we can draw from the aharonovbohm effect. Does this effect has anything to do with the topology of the space. Does it simply suggest that the vector potential has measurable effects. Nearinfrared magnetooptical spectroscopy of singlewalled carbon nanotubes reveals two absorption peaks with an equal strength at high magnetic.
As such, the ab effect can be described as a holonomy. The effect was confirmed by many different experiments and today its existence is widely accepted. Evidence for dark excitons in a single carbon nanotube due. Effects of electronphonon interaction on optical phonons are studied in carbon nanotubes. The proposed device is made of a short singlewalled carbon nanotube swcnt placed on a substrate and coupled to a tipcontacts. Us201001402a1 apparatus for manufacturing carbon nano. Optical absorption spectra are calculated in carbon nanotubes in the presence of a magnetic flux parallel to the tube axis. Physica b 201 1994 349352 aharonovbohm effect in carbon nanotubes hiroshi ajiki, tsuneya ando institute for solid state physics, university of tokyo, 7221 roppongi, minatoku, tokyo 106, japan abstract optical absorption spectra are calculated in carbon nanotubes in the presence of a magnetic flux parallel to the tube axis.
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