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Acoustic phonons propagating in semiconductor quantum wires and their mean-free-path

半导体量子线中传播的声声子及其平均自由程

基本信息

批准号：
08650061
负责人：
NISHIGUCHI Norihiko
金额：
$ 1.41万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

In this work, we obtained normal acoustic phonon modes of rectangular quantum wires, applying an algorithm referred to as the xyz algorithm which is used in the ultrasonic sound spectroscopy. The normal modes are classified, according to the spatial symmetries of the rectangular wires, into the dilatational, shear/torsional, and flexural modes. The shear/torsional mode is not well defined for rectangular wires, but they are well defined for square wires.Dispersion curves of these modes have phonon subbands caused by the phonon confinement in the lateral direction of the wires. We investigated electron scattering by these acoustic phonon modes via the deformation potential and the suface vibrations induced by acoustic phonons. The latter is termed the ripple mechanism after the light scattering from vibrating surface. Paying special attention to coherence among the scattering events, we found the deformation potential and the ripple mechanism scatterings take place only for the dilatational phonon mode and therefore these two kinds of scatterings interfere to enhance scattering rates.Consequently, the scattering rates are more enhanced than the sum of individual contribution of these mechanisms to electron scatterings. This coherent interference between the deformation potential and the ripple mechanism scatterings is not peculiar to the rectangular quantum wires, but bring about for other systems with low spatial symmetries. This leads to the conclusion that the coherent interference between these two electron-phonon interaction is essential to the electron systems confined in the nanostructures, suggesting that the deformation potential can be empirically changed to incorporate the effect of the surface vibrations on the electron-phonon interaction.

在这项工作中，我们应用超声声谱中的XYZ算法，得到了矩形量子线的正常声子声子模。根据矩形导线的空间对称性，将简正波分为伸缩、剪切/扭转和弯曲三种。对于矩形导线，剪切/扭转模式没有很好的定义，而对于方形导线，剪切/扭转模式被很好地定义，这些模式的色散曲线上有声子子带，这是由于声子在导线的横向方向上的限制造成的。我们通过形变势和声学声子引起的表面振动研究了这些声学声子模的电子散射。后者是根据振动表面的光散射而产生的波纹机制。特别注意散射事件之间的相干性，我们发现形变势和波纹机制的散射只在膨胀声子模式下发生，因此这两种散射相互干扰，提高了散射率，从而使散射率的提高比这两种机制对电子散射的贡献之和更大。这种形变势和波纹机制散射之间的相干干涉并不是矩形量子线所特有的，而是对其他空间对称性较低的系统也是如此。由此得出结论，这两个电子-声子相互作用之间的相干干涉对于限制在纳米结构中的电子系统是必不可少的，这表明可以经验地改变形变势以考虑表面振动对电子-声子相互作用的影响。