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

在这项工作中，我们获得了正常的声学声子模式的矩形量子线，应用算法称为xyz算法，这是用于超声声波光谱。根据矩形线的空间对称性，将简正模式分为弯曲模式、剪切/扭转模式和弯曲模式。剪切/扭转模在矩形线中没有很好的定义，但在方形线中很好的定义，这些模的色散曲线都有声子子带，这是由于线的横向声子限制引起的。我们通过形变势和声子诱导的表面振动研究了这些声子模对电子的散射。后者被称为涟漪机制后，从振动表面的光散射。特别注意散射事件之间的相干性，我们发现形变势和涟漪机制散射只发生在双声子模上，因此这两种散射相互干扰，使散射率增加，从而使散射率的增加大于这两种机制对电子散射的单独贡献之和。这种形变势与涟漪机制散射之间的相干干涉并不是矩形量子线所特有的，而是其他具有低空间对称性的系统所特有的。这导致的结论是，这两个电子-声子相互作用之间的相干干涉是必不可少的电子系统限制在纳米结构中，这表明可以根据经验改变变形电位，以纳入电子-声子相互作用的表面振动的效果。

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.