Indirect interband transition induced by optical near fields with large wave numbers
Indirect interband transition induced by optical near fields with large wave numbers
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DOI：
10.1103/physrevb.93.195111
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发表时间：
2016-05-06
影响因子：
3.7
通讯作者：
Nobusada, Katsuyuki
中科院分区：
文献类型：
--
作者：
Yamaguchi, Maiku;Nobusada, Katsuyuki
光学近场具有大波数的傅里叶分量，由于其在空间上的不均匀性，其波数比远场传输光的波数大两到三个数量级。通过利用这些大的波数，ONF有望在具有不同波数的Bloch态之间产生间接的带间跃迁，并直接产生电子-空穴对，而不需要电子-声子耦合。我们对具有间接带隙结构的一维周期势进行了含时动力学计算，证明了ONF确实诱导了间接带间跃迁。我们没有使用常规能带结构计算中通常强加的一般Bloch边界条件，而是采用了另一种边界条件，Born-von Karman边界条件，以适当地处理间接带间跃迁。计算的远场和ONF激发的吸收光谱显示出不同的吸收边和光谱模式。我们认为，这种差异可以通过实验测量，作为ONF大波数效应的证据。
Optical near fields (ONFs) have Fourier components with large wave numbers that are two or three orders of magnitude larger than those of far-field propagating light owing to their nonuniformity in space. By utilizing these large wave numbers, the ONF is expected to induce an indirect interband transition between Bloch states having different wave numbers and directly generate an electron-hole pair without electron-phonon coupling. We perform time-dependent dynamics calculations of a one-dimensional periodic potential with an indirect band-gap structure and demonstrate that the ONF definitely induces an indirect interband transition. Instead of using the general Bloch boundary condition, which is usually imposed in conventional band structure calculations, we adopt an alternative boundary condition, the Born-von Karman boundary condition, to appropriately treat indirect interband transitions. The calculated absorption spectra for the far-field and ONF excitations show different absorption edges and spectral patterns. We argue that this difference can be experimentally measured as evidence of the effects of the large wave numbers of the ONF.