期刊
PHYSICAL REVIEW LETTERS
卷 96, 期 12, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.96.126104
关键词
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We show that the optical absorption spectra of boron nitride (BN) nanotubes are dominated by strongly bound excitons. Our first-principles calculations indicate that the binding energy for the first and dominant excitonic peak depends sensitively on the dimensionality of the system, varying from 0.7 eV in bulk hexagonal BN via 2.1 eV in the single sheet of BN to more than 3 eV in the hypothetical (2,2) tube. The strongly localized nature of this exciton dictates the fast convergence of its binding energy with increasing tube diameter towards the sheet value. The absolute position of the first excitonic peak is almost independent of the tube radius and system dimensionality. This provides an explanation for the observed optical gap constancy for different tubes and bulk hexagonal BN.
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