Electron-Phonon Interaction and Magnetophonon Resonance in Quantum Wires

量子线中的准一维电子在输运和光性质上具有各种有趣的特征。这种电子气体可以通过使用栅极或蚀刻侧壁来收缩异质界面中的二维电子气体来形成。由于态密度的奇异性，这种准一维电子气体表现出不同的电子-声子相互作用，因此我们可以期待电子传递的一个非常有趣的特征。众所周知，在低温下，这类电子表现出弹道输运、干涉效应、电导率量子化、量子涨落等特性。本课题主要研究高温下量子线中电子-声子相互作用的研究，以及磁声子共振的理论表述和实验观察。所得结果总结如下：1。用Kubo公式推导了准一维电子气体的磁导率。在具有抛物线约束势，能量间隔为hOMEGA的窄量子线中，磁导率在共振处呈现极值NhROO<W^2_+OMEGA^2>=hw_o，其中w_c=eB/m^*， N=1,2,3，磁导率由两个主要项组成，一个是sigma_<ep>，这是由于位于量子线中心附近的电子被LO声子散射导致磁导率在共振处达到最大值；Sigma_ <po>，这是由于电子在量子线边缘附近的跳跃运动所引起的扰动，使其磁导率达到极小值。在不同结构的量子线中进行的实验表明，在100-200K的温度范围内，磁阻达到最大值（p_<xx>=1/sigma_<xx>），表明sigma_<po>占主导地位。2. 采用电子束光刻和激光束全息技术制备量子线。我们还制备了用于处理量子线的光学掩模。3. 实验观测发现，在4.2 K时存在明显的舒布尼科夫-德哈斯振荡，在更高温度下存在明显的振荡结构，与理论预测吻合较好。分析给出了有效质量和约束势。4. 我们用肖特基门制备了量子线，低温测量得到了约束势为05 meV.5的电子的准一维性质。我们对高磁场下的GaAs/AlAs短周期超晶格进行了回旋共振测量，并观察到了带折叠X_z导带中电子的共振。我们发现G和X_z导带的交叉发生在单层数n=12.6处。我们制作了GaAs/AlAs超晶格的p-i-n二极管，并成功地首次观察到与Wannier-Stark态相关的齐纳隧道效应。少

Quasi-one-dimensional electrons in quantum wires give various interesting features in transport and optical properties. Such electron gas may be formed by constricting two-dimensional electron gas in heterointerfaces by using gate electrodes or by etching the side walls. Such Quasi-one-dimensional electron gas exhibit different electron-phonon interactions due to the singularity of the density of states, and thus we can expect a very interesting feature of electron transport. At low temperatures, it is well known that such electrons show ballistic transport, interference effects, quantization of conductivity, quantum fluctuation and so on. In this research project we will concern with investigation of electronphonon interaction in quantum wires at high temperatures and also with theoretical formulation and experimental observation of magnetophonon resonance. The obtained results are summarized in the following.1. We derived magnetoconductivity of quasi-one-dimensional electron gas by u … More sing Kubo formula. In a narrow quantum wire with parabolic confinement potential, energy spacing hOMEGA, the magnetoconductivity exhibits extrema at resonance NhROO<W^2_+OMEGA^2>=hw_o, where w_c=eB/m^* and N=1,2,3, -The magnetoconductivity is found to consist of two dominant terms, the one, sigma_<ep>, due to the scattering of electrons located near the center of the quantum wire by LO phonons resulting in maxima of the magnetoconductivity at the resonance, and the other, sigma_<po> due to the disturbance of the skipping motion of electrons near the edge of the quantum wire giving rise to minima in the magnetoconductivity. Experiments have been carried out in quantum wires with different structures, and revealed maxima in the magnetorisistance(p_<xx>=1/sigma_<xx>)in the temperature range 100-200K,which indicates the term sigma_<po> dominates. 2. We fabricated quantum wires by using electron beam lithography and by laser beam holography. Also we prepared optical masks for processing quantum wires. 3. Experimental observation revealed clear Shubnikov-de Haas oscillations at 4.2 K and clear oscillatory structures at higher temperatures, which show a good agreement with the theoretical prediction. The analysis gives the effective mass and confinement potential. 4. We prepared quantum wires with Schottky gates and low temperature measurements gives quasi-one-dimensional nature of electrons with confinement potential of 05 meV.5. We carried out cyclotron resonance measurements of GaAs/AlAs short period superlattices at high magnetic fields and observed the resonance of electrons in the zone-folded X_z conduction band. We found that the cross-over of the G and X_z conduction bands occur at the monolayr number n=12.6. We fabricated p-i-n diodes of GaAs/AlAs superlattices and succeeded in the first observation of Zener tunneling associated with Wannier-Stark states. Less