P. J. Michalski

University of Pennsylvania, Philadelphia, PA, United States

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Publications (5)15.27 Total impact

  • P. J. Michalski, E. J. Mele
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    ABSTRACT: We calculate effects of an applied helically symmetric potential on the low energy electronic spectrum of a carbon nanotube in the continuum approximation. The spectrum depends on the strength of this potential and on a dimensionless geometrical parameter, P, which is the ratio of the circumference of the nanotube to the pitch of the helix. We find that the minimum band gap of a semiconducting nanotube is reduced by an arbitrarily weak helical potential, and for a given field strength there is an optimal P which produces the biggest change in the band gap. For metallic nanotubes the Fermi velocity is reduced by this potential and for strong fields two small gaps appear at the Fermi surface in addition to the gapless Dirac point. A simple model is developed to estimate the magnitude of the field strength and its effect on DNA-carbon nanotube complexes in an aqueous solution. We find that under typical experimental conditions the predicted effects of a helical potential are likely to be small and we discuss several methods for increasing the size of these effects.
    Physical review. B, Condensed matter 02/2008; 77(8). · 3.77 Impact Factor
  • Source
    P. J. Michalski, Eugene J. Mele
    [Show abstract] [Hide abstract]
    ABSTRACT: We calculate effects of an applied helically symmetric potential on the low energy electronic spectrum of a carbon nanotube in the continuum approximation. The spectrum depends on the strength of this potential and on a dimensionless geometrical parameter, P, which is the ratio of the circumference of the nanotube to the pitch of the helix. We find that the minimum band gap of a semiconducting nanotube is reduced by an arbitrarily weak helical potential, and for a given field strength there is an optimal P which produces the biggest change in the band gap. For metallic nanotubes the Fermi velocity is reduced by this potential and for strong fields two small gaps appear at the Fermi surface in addition to the gapless Dirac point. A simple model is developed to estimate the magnitude of the field strength and its effect on DNA-carbon nanotube complexes in an aqueous solution. We find that under typical experimental conditions the predicted effects of a helical potential are likely to be small and we discuss several methods for increasing the size of these effects.
    Department of Physics Papers. 01/2008;
  • P. J. Michalski, E. J. Mele
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    ABSTRACT: We develop and solve a continuum theory for the piezoelectric response of nanotubes under applied uniaxial and torsional stresses. We find that the piezoelectric response is controlled by the chiral angle, the aspect ratio, and two dimensionless parameters specifying the ratio of the strengths of the electrostatic and elastic energies. The model is solved in two limiting cases and the solutions are discussed. These systems are found to have several unexpected physical effects not seen in conventional bulk systems, including a strong stretch-twist coupling and the development of a significant bound charge density in addition to a surface charge density. The model is applied to estimate the piezoelectric response of a boron nitride nanotube under uniform tensile stress.
    Physical review. B, Condensed matter 11/2007; 76(20). · 3.77 Impact Factor
  • Source
    P J Michalski, Na Sai, E J Mele
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    ABSTRACT: We develop and solve a continuum theory for the piezoelectric response of one-dimensional nanotubes and nanowires, and apply the theory to study electromechanical effects in boron-nitride nanotubes. We find that the polarization of a nanotube depends on its aspect ratio, and a dimensionless constant specifying the ratio of the strengths of the elastic and electrostatic interactions. The solutions of the model as these two parameters are varied are discussed. The theory is applied to estimate the electric potential induced along the length of a boron-nitride nanotube in response to a uniaxial stress.
    Physical Review Letters 10/2005; 95(11):116803. · 7.73 Impact Factor
  • Source
    Paul Joseph Michalski, Eugene J Mele
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    ABSTRACT: We develop and solve a continuum theory for the piezoelectric response of nanotubes under applied uniaxial and torsional stresses. We find that the piezoelectric response is controlled by the chiral angle, the aspect ration, and two dimensionless parameters specifying the ratio of the strengths of the electrostatic and elastic energies. The model is solved in two limiting cases and the solutions are discussed. These systems are found to have several unxpected physical effects not seen in conventional bulk systems, including a strong stretch-twist coupling and the development of a signficant bound charge density in addition to a surface charge density.
    Department of Physics Papers.

Publication Stats

12 Citations
15.27 Total Impact Points

Institutions

  • 2005–2008
    • University of Pennsylvania
      • Department of Physics and Astronomy
      Philadelphia, PA, United States