Interacting Two-dimensional Electrons in Unconventional Systems

****技术摘要****本研究探索高质量、量子限制半导体结构中的电子相互作用物理。该计划包括通过分子束外延技术制造的研究，以及电子相关现象占主导地位的低温和高磁场下的电子传输特性。这项工作的重点是新颖的、高质量的二维电子系统，局限于选择性掺杂的AlAs和宽GaAs量子阱。砷化镓中的二维电子具有与砷化镓中的标准二维电子非常不同的参数：它们具有更大的各向异性有效质量，更大的有效g因子，并且它们占据多个导带谷。另一方面，宽砷化镓阱中的电子系统具有厚的或双层状的电荷分布，并且可以占据两个电子带。因此，AlAs和宽砷化镓二维电子都为新的多体物理提供了至关重要的实验平台。本项目将研究几个问题，包括谷、子带、层和自旋自由度在决定电子系统基态中的作用。该项目将由研究生和本科生进行，他们将接受晶体生长、制造和电气测量等关键领域的培训。****非技术摘要****固态物理学中最引人入胜的领域之一涉及主要由于带电粒子（如电子）之间的相互作用而产生的物质的新状态。为了探索这种状态，我们需要将样品中的缺陷（包括杂质和晶体缺陷）减少到最小。这项研究涉及到这种样品的制造，以及它们的新电子特性的测量。重点是局限于砷化铝或砷化镓量子阱的二维电子系统。这些材料的参数与通常研究的样品非常不同，并为我们提供了具有额外电子自由度的系统，如自旋，层和谷。对新样品中观察到的状态和现象的理解不仅会提高我们对基础物理学的认识，而且还会导致新的设备概念。这项研究的一个主要组成部分是在晶体生长、半导体样品处理和电测量等关键领域对研究生和本科生进行培训和教育。在这一领域训练有素的学生将是美国和世界其他地区的宝贵资源。

****Technical Abstract****This study explores electron interaction physics in high-quality, quantum-confined semiconductor structures. The program includes studies of both fabrication, via the molecular beam epitaxy technique, and of electronic transport properties at low temperatures and high magnetic fields where electron correlation phenomena dominate. The emphasis of the work is on novel, high-quality two-dimensional electron systems confined to selectively-doped AlAs and wide GaAs quantum wells. The two-dimensional electrons in AlAs have parameters that are very different from those of the standard two-dimensional electrons in GaAs: they have a much larger and anisotropic effective mass, a much larger effective g-factor, and they occupy multiple conduction band valleys. The electron systems in wide GaAs wells, on the other hand, have thick or bilayer-like charge distributions and can occupy two electric subbands. Both AlAs and wide GaAs two-dimensional electrons thus provide crucial and important test-beds for new many-body physics. Several problems will be studied in the course of this project, including the role of valley, subband, layer, and spin degrees of freedom in determining the electron system's ground states. The project will be carried out by graduate and undergraduate students who will be trained in crucial areas of crystal growth, fabrication, and electrical measurements. ****Non-Technical Abstract****One of the most fascinating areas in solid state physics concerns new states of matter that come about primarily because of the interaction between charged particles such as electrons. To explore such states, one needs specimens in which the imperfections, including impurities and crystal defects, are reduced to a minimum. This study involves the fabrication of such samples, and measurements of their novel electronic properties. The emphasis is on two-dimensional electron systems confined to aluminum-arsenide or gallium-arsenide quantum wells. These materials have parameters that are very different from the commonly studied samples, and provide us with systems that have extra electronic degrees of freedom, such as spin, layer, and valley. An understanding of the states and phenomena observed in the new samples not only will advance our knowledge of fundamental physics, but can also lead to novel device concepts. A major component of this research is the training and education of graduate and undergraduate students in critical areas of crystal growth, semiconductor sample processing, and electrical measurements. Well-trained students in this field will be invaluable resources for the US as well as the rest of the world.