单壁磁性纳米管的自旋波谱

Spin Waves in Ferromagnetic Single-walled Nanotubes

利用量子统计理论的多体格林函数方法计算了单壁磁性纳米管的自旋波的色散关系.Armchair型纳米管的自旋波谱只有一支,这一支有int(m/2+1)条色散曲线.当q1a+q2a=2π时,自旋波能量是简并的.当纳米管的管径m(亦即圆周方向上的格点数)一定时,自旋波能量曲线随温度的升高而降低.Zigzag型磁纳米管的自旋波谱分为两支:ω1支和ω2支.每一支都有m条色散曲线.当q1b+q2b=π时,自旋波能量是简并的.自旋波能量简并在物理上是由对称性所致.

The spin wave spectra of ferromagnetic single-walled nanotubes are calculated by use of the many-body Green＇s function method of quantum statistical theory.For a nanotube of armchair type with a diameter m,there is the only one category of energy spectra,which contains int[m/2＋1] branches of energy spectra.As q1a＋q2a=2π,the spin wave energy is degenerate.When the diameter m of a nanotube is fixed,a higher temperature leads to lower energy spectra.For a nanotube of zigzag type with a diameter m,energy spectra are classified into two categories,ω1and ω2.Each of them has m branches of energy spectra.As q1b＋q2b=π,the spin wave spectra of the tubes are degenerate,which is caused by the symmetry physically.