我們使用sp3的緊束模型去計算單層奈米碳微管在均勻的橫向電場和任意角度磁場下的能帶結構。能帶的色散關係、能隙、能帶的邊界態和簡併度都與場的強度、方向以及幾何結構(半徑和螺旋的角度)有密切的關係。電場會使窄能隙和中等能隙發生半導體和金屬的轉換，而金屬性的手椅狀碳微管則不會有這樣的現象。磁場會破壞簡併度，主要是由於平行管軸的方向所貢獻。電子性質會反應在態密度上，拋物線的能帶會在態密度上出現峰值，線性交叉的能帶反映在態密度上則是平的情形。

We use the sp3 tight-binding model to calculate band structures of single-walled carbon nanotubes under uniform transverse electric fields and magnetic fields with different gazing angles. Energy dispersion, energy gaps, band-edge states, state degeneracy, and subband spacing, are very sensitive to the changes in the field strength and geometric structures (radii and chiral angles). The electric field could make narrow-gap and moderate-gap carbon nanotubes exhibit the semiconductor-metal transitions. Such transitions are absent in metallic armchair carbon nanotubes. State degeneracy could be broken due to parallel magnetic fields. The electronic properties will be reflected in the density of states (DOS). The peak positions correspond to the band-edge states while the corresponding DOS for linear subbands is a constant value.

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