We investigate how the orbital magnetic moments of electron and hole states in a carbon nanotube quantum dot depend on the number of carriers on the dot. Low temperature transport measurements are carried out in a setup where the device can be rotated in an applied magnetic field, thus enabling accurate alignment with the nanotube axis. The field dependence of the level structure is measured by excited state spectroscopy and excellent correspondence with a single-particle calculation is found. In agreement with band structure calculations we find a decrease of the orbital magnetic moment with increasing electron or hole occupation of the dot, with a scale given by the band gap of the nanotube.

/pdf/gate-dependent-orbital-magnetic-moments-in-carbon-nanotubes-3zbputhhxl.pdf

Gate-dependent orbital magnetic moments in carbon nanotubes.

Nonlinear optical absorption in graphene via two-photon absorption process

Carbon-based materials offer a number of exciting possibilities for both new science and applications. Many of these are based on the novel band structure of graphene, by which solids mimic the properties of relativisitic fermions and which offers the potential for high speed nanoscale electronics. When sheets of graphene are rolled up to make carbon nanotubes, further interesting properties are found; for example, both semiconducting and metallic nanotubes able to be produced. The novel properties of these new materials, together with the already remarkable properties of diamond itself, are discussed by a series of experts who came together in May 2007 to discuss and debate the potential for future development.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2007.2160

Introduction. Carbon-based electronics: fundamentals and device applications

Experimental study of Coulomb corrections and single-particle energies for single-walled carbon nanotubes using cross-polarized photoluminescence

Graphene is known to show a significant photo-thermoelectric effect that can exceed its photovoltaic contribution. Here, by utilizing this effect, we demonstrate a photovoltage measurement of cyclotron resonance in a double-back-gated h-BN/graphene/h-BN two-terminal device. A graphite local bottom gate was fabricated in addition to a p-doped Si global back gate. By tuning the two gate voltages, an in-plane graphene junction having an asymmetric carrier-doping profile was created. With the help of this asymmetric structure, the photo-thermoelectric voltage generated in the vicinity of the metal-electrode/graphene junction was detected. At a low temperature and in the presence of a magnetic field, a photo-induced voltage was measured under the irradiation of an infrared laser (λ = 9.28–10.61 μm). We observed a strong enhancement of the photovoltage signal under the cyclotron resonance condition, at which the energy of excitation coincides with a transition between Landau levels. These results highlight the possibility of using the photo-thermoelectric effect in graphene for THz photo-detection.

Photo-thermoelectric detection of cyclotron resonance in asymmetrically carrier-doped graphene two-terminal device

We report studies of cyclotron resonance in monolayer graphene. Cyclotron resonances are detected by observing changes in the photoconductive response of the sample. An electron velocity at the Dirac point of 1.093 x 10(6) m s(-1) is obtained, which is the fastest velocity recorded for all known carbon materials. In addition, a significant asymmetry exists between band structure for electrons and holes, which gives rise to a 5% difference between the velocities at energies of 125 meV away from the Dirac point.

/pdf/cyclotron-resonance-of-electrons-and-holes-in-graphene-2xrwgzxh4x.pdf

Russell S. Deacon

Papers

Cyclotron resonance of electrons and holes in graphene monolayers