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Title: Broken symmetry and pseudogaps in ropes of carbon nanotubes

Abstract

We investigate the influence of tube-tube interactions in ropes of (10,10) carbon nanotubes, and find that these effects induce a pseudogap in the density of states (DOS) of the rope of width 0.1 eV at the Fermi level. In an isolated (n,n) carbon nanotube there are two bands that cross in a linear fashion at the Fermi level, making the nanotube metallic with a DOS that is constant in a 1.5 eV wide window around the Fermi energy. The presence of the neighbouring tubes causes these two bands to repel, opening up a band gap that can be as large as 0.3 eV. The small dispersion in the plane perpendicular to the rope smears out this gap for a rope with a large cross-sectional area, and we see a pseudogap at the Fermi energy in the DOS where the DOS falls to one third of its value for the isolated tube. This phenomenon should affect many properties of the behavior of ropes of (n,n) nanotubes, which should display a more semimetallic character than expected in transport and doping experiments, with the existence of both hole and electron carriers leading to qualitatively different thermopower and Hall-effect behaviors from those expected formore » a normal metal. Band repulsion like this can be expected to occur for any tube perturbed by a sufficiently strong interaction, for example, from contact with a surface or with other tubes. {copyright} {ital 1999} {ital The American Physical Society}« less

Authors:
; ; ; ;  [1]
  1. Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States)|[Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
686459
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter
Additional Journal Information:
Journal Volume: 60; Journal Issue: 11; Other Information: PBD: Sep 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; SYMMETRY BREAKING; ENERGY GAP; ENERGY-LEVEL DENSITY; ELECTRONIC STRUCTURE; FERMI LEVEL; HALL EFFECT; ELECTRIC CONDUCTIVITY

Citation Formats

Delaney, P., Joon Choi, H., Ihm, J., Louie, S.G., and Cohen, M.L. Broken symmetry and pseudogaps in ropes of carbon nanotubes. United States: N. p., 1999. Web. doi:10.1103/PhysRevB.60.7899.
Delaney, P., Joon Choi, H., Ihm, J., Louie, S.G., & Cohen, M.L. Broken symmetry and pseudogaps in ropes of carbon nanotubes. United States. doi:10.1103/PhysRevB.60.7899.
Delaney, P., Joon Choi, H., Ihm, J., Louie, S.G., and Cohen, M.L. Wed . "Broken symmetry and pseudogaps in ropes of carbon nanotubes". United States. doi:10.1103/PhysRevB.60.7899.
@article{osti_686459,
title = {Broken symmetry and pseudogaps in ropes of carbon nanotubes},
author = {Delaney, P. and Joon Choi, H. and Ihm, J. and Louie, S.G. and Cohen, M.L.},
abstractNote = {We investigate the influence of tube-tube interactions in ropes of (10,10) carbon nanotubes, and find that these effects induce a pseudogap in the density of states (DOS) of the rope of width 0.1 eV at the Fermi level. In an isolated (n,n) carbon nanotube there are two bands that cross in a linear fashion at the Fermi level, making the nanotube metallic with a DOS that is constant in a 1.5 eV wide window around the Fermi energy. The presence of the neighbouring tubes causes these two bands to repel, opening up a band gap that can be as large as 0.3 eV. The small dispersion in the plane perpendicular to the rope smears out this gap for a rope with a large cross-sectional area, and we see a pseudogap at the Fermi energy in the DOS where the DOS falls to one third of its value for the isolated tube. This phenomenon should affect many properties of the behavior of ropes of (n,n) nanotubes, which should display a more semimetallic character than expected in transport and doping experiments, with the existence of both hole and electron carriers leading to qualitatively different thermopower and Hall-effect behaviors from those expected for a normal metal. Band repulsion like this can be expected to occur for any tube perturbed by a sufficiently strong interaction, for example, from contact with a surface or with other tubes. {copyright} {ital 1999} {ital The American Physical Society}},
doi = {10.1103/PhysRevB.60.7899},
journal = {Physical Review, B: Condensed Matter},
number = 11,
volume = 60,
place = {United States},
year = {1999},
month = {9}
}