【作者】 高宏雷；

【导师】 高洁；

【作者基本信息】 四川大学 ， 凝聚态物理， 2004， 硕士

【摘要】 20世纪80年代初期开始兴起的介观物理是凝聚态物理中人们十分关注的领域,介观物理揭示了许多新的物理效应,对物理基础理论、实验测量和半导体器件的发展都有重要意义。近年来,介观系统中表面声波对单个电子的输运问题引起了人们极大的兴趣。1996年剑桥大学凯文迪什实验室的Pepper小组在实验中观察到,表面声波在GaAs/AlxGa1-xAs异质结表面上沿由分裂门产生的准一维电子通道方向传播时,在通道内诱导产生的声电电流随门电压振荡,且在一维通道钳断的情况下,声电电流是量子化的,其值为,其中为正整数,为表面声波的频率,是电子电荷。该量子化的声电电流有可能作为量子电流标准,与根据约瑟夫森效应建立起来的量子电压标准和由量子霍尔效应建立起来的量子电阻标准一起构成封闭的“计量三角形”。这对于介观量子输运理论和计量学的发展都具有极其重要的意义。表面声波与GaAs/AlxGa1-xAs异质结中二维电子气相互作用过程中,电子在GaAs/AlxGa1-xAs异质结二维电子气中的准一维电子通道内的运动为弹道式的,并且电子在一维通道边界上的散射为镜面反射,因此,低维系统表面声波对电子的输运现象可以简化为准一维系统中的电子弹道输运问题。我们采用WKB近似计算出表面声波在GaAs/AlxGa1-xAs异质结表面沿由分裂门产生的准一维电子通道方向传播时,量子阱捕获一个电子和两个电子时的声电电流;并详细讨论了表面声波的频率和功率,以及分裂门偏压、库仑相互作用和源漏偏压对声电电流的影响,为进一步的实验工作提供有益指导和参考。更多还原

【Abstract】 The study of electron transport in mesoscopic systems has recently attracted much attention. Some new phenomena have been found in the experiment about mesoscopic systems. In 1996, the group Pepper of Cavendish Laboratory not only observed the giant oscillation in the acoustoelectric current induced by the surface acoustic wave (SAW) as function of the split gate voltage when SAW launched along the quasi-one-dimensional electron channel defined in a GaAs/AlxGa1-xAs heterostructure by split gate but also found that the acoustoelectric current I versus the split gate voltage displayed a step-like behavior and the values of the current on the plateaus are quantized with , where is electron charge, is the SAW frequency, and is the number of electrons captured in the quantum well when the quasi-one-dimensional channel was pinched off. This observation not only has great significance on the theory of mesoscopic transport but also may afford an accurate standard of current. The realization of a standard of current is important because it would close the “metrological triangle” of resistance, voltage and current measurements or could alternatively be used to obtain a measure of the charge of an electron.The electron transport in a quasi-one-dimensional channel defined in a GaAs/AlxGa1-xAs heterostructure by split gate could be considered as the electron ballistic transport. Using the WKB approximation, we calculated the acoustoelectric <WP=4>current when only one electron was captured in the quantum well and discussed the effect on the acoustoelectric current caused by SAW power, SAW frequency, split gate voltage and Source-Drain bias. Based on this result, we considered the case when two interacting electrons were captured in the quantum well and analyzed the effect on the acoustoelectric current caused by the Coulomb interaction between electrons in the quantum well and Source-Drain bias.更多还原