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ABSTRACT: In this work, we use the tight-binding model to study the low-energy electronic properties of carbon nanoscrolls subject to the influences of a transverse electric field. A carbon nanoscroll can be considered as an open-ended spirally wrapped graphene nanoribbon. The inter-wall interactions will alter the subband curvature, create additional band-edge states, modify the subband spacing or energy gap, and separate the partial flat bands. Furthermore, the energy band symmetry about the Fermi level is lifted by such interactions. The truncated Archimedean spiral ρ = r a θ +r is used to describe the spiral structures of carbon nanoscrolls. The energy gap is found to oscillate significantly with r, and exhibits complete energy gap modulations. With the inclusion of a transverse electric field, the band structures are further altered. Inter-wall hoppings will cause electron transfers between different atoms leading to distortions of the electron wavefunctions. The main features of the energy dispersions are directly reflected in the density of states. The numbers, heights, and energies of the density of states peaks are dependent on the electric field strength.
Philosophical Magazine 04/2011; 91(11):1557-1567. · 1.51 Impact Factor
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ABSTRACT: The electronic and optical properties of monolayer and bilayer graphene are investigated to verify the effects of interlayer interactions and external magnetic field. Monolayer graphene exhibits linear bands in the low-energy region. Then the interlayer interactions in bilayers change these bands into two pairs of parabolic bands, where the lower pair is slightly overlapped and the occupied states are asymmetric with respect to the unoccupied ones. The characteristics of zero-field electronic structures are directly reflected in the Landau levels. In monolayer and bilayer graphene, these levels can be classified into one and two groups, respectively. With respect to the optical transitions between the Landau levels, bilayer graphene possesses much richer spectral features in comparison with monolayers, such as four kinds of absorption channels and double-peaked absorption lines. The explicit wave functions can further elucidate the frequency-dependent absorption rates and the complex optical selection rules. These numerical calculations would be useful in identifying the optical measurements on graphene layers.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 12/2010; 368(1932):5445-58. · 2.77 Impact Factor
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ABSTRACT: This study shows that a spatially modulated sinusoidal electric field can significantly tune the magneto-absorption spectra of a graphene ribbon. The pattern of absorption spectra evolves with the amplitude of electric potential (V0). When V0 is weaker than the state energy of the first Landau level, E1, the modulated electric field not only changes the peak intensity and peak position of the absorption lines, but also generates new peaks. These additional peaks follow the unusual optical selection rule. When V0 is stronger than E1, the intensity of original peaks, induced by the uniform magnetic field, shrinks, and an anomalous lowest peak appears. Most importantly, the energy position of the first peak strongly depends on both the amplitude of the electric potential and the strength of the magnetic field. These characteristics can be used to modulate the threshold frequency of the magneto-absorption spectra.
09/2010;
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ABSTRACT: The low-energy magnetoelectronic structures of nanographene ribbons under a modulated magnetic field are investigated by the Peierls tight-binding model. They are dominated by the field strength, period, phase, the ribbon width, and edge structure. The modulated magnetic field could add state degeneracy, modify energy dispersions, alter subband spacings, affect carrier-density distributions, create additional band-edge states, and cause semiconductor-metal transitions. The main features of energy bands are directly reflected in density of states, such as the position, height, structure, and number of the prominent peaks. These results immensely differ from those in a uniform magnetic field. Significant differences between a 1D graphene ribbon and a 2D electron gas are also found.
Journal of Nanoscience and Nanotechnology 06/2009; 9(5):3193-200. · 1.56 Impact Factor
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ABSTRACT: The low energy magnetoelectronic structures for a nanographene ribbon under modulated magnetic fields are investigated through the Peierls tight-binding model. They are dominated by the field strength, period, phase, the ribbon width, and edge structure. The modulated magnetic field could add state degeneracy, modify energy dispersions, alter subband spacings, affect carrier-density distributions, create additional band-edge states, and extend the partial flat bands. The main features of energy bands are directly reflected in density of states, such as the position, the height, the structure, and the number of the prominent peaks. These results are compared with a zigzag ribbon under a uniform magnetic field. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 09/2008; 245(12):2761 - 2765. · 1.32 Impact Factor
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ABSTRACT: The effects of the modulated magnetic field on one dimension at energy bands of nanographite ribbons are investigated by the Peierls tight-binding model. Electronic properties strongly depend on the strength and the period of the modulated magnetic field, the ribbon width, and the edge structure. The modulated magnetic field could destroy state degeneracy, modify energy dispersions, alter subband spacings, affect wave functions, create additional band-edge states, and cause semiconductor–metal transitions. The main features of energy bands are directly reflected in density of states, such as the number, the positions, the heights, and divergent structures of the prominent peaks. © 2007 Published by Elsevier B.V.
Physics Letters A. 01/2007; 3692021(73).
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ABSTRACT: The effects of the modulated magnetic field on one dimension at energy bands of nanographite ribbons are investigated by the Peierls tight-binding model. Electronic properties strongly depend on the strength and the period of the modulated magnetic field, the ribbon width, and the edge structure. The modulated magnetic field could destroy state degeneracy, modify energy dispersions, alter subband spacings, affect wave functions, create additional band-edge states, and cause semiconductor–metal transitions. The main features of energy bands are directly reflected in density of states, such as the number, the positions, the heights, and divergent structures of the prominent peaks.
Physics Letters A.
