CAREER: Hybrid Systems of Al/AlOx/Al Tunnel Junctions Coupled to Semiconductor Heterostructures

该项目的中心是Al/AlOx/Al隧道结与半导体异质结耦合的混合系统。已知Al/AlOx/Al隧道结的阵列形成具有表现为量子力学的宏观自由度的系统。通过在GaAs/AlGaAs异质结上制造这样的隧道结系统，电子气位于异质结的顶面附近，我们可以直接控制耗散，而不依赖于其他参数，这在任何量子系统中都是不可能的。该项目的目标之一是在各种结构中实现对耗散的控制，以研究基本的隧穿过程和量子相变。在半导体方面，混合电路也使许多独特的和潜在的重要实验成为可能。特别是，我们将使用混合研究两个最基本的方面，电荷和统计，分数量子霍尔液体（HLS）的激发。值得注意的是，被称为Laughlin准粒子（Laughlin quasiparticles）的激发被预测携带分数电荷，并且服从与费米子或玻色子不同的不寻常的分数统计。分数统计的测量，我们希望解决使用Al/AlOx/Al隧道结，一直是分数量子霍尔效应领域的一个长期挑战。这项研究将伴随着一个全国性的推广计划，全国各地的高中生将进行合作测量，以确定北磁极的位置。在全球范围内进行测量将提供有趣和真实的科学体验，我们希望这将激发学生对科学的兴趣。%典型的宏观物体，如尘埃粒子、台球和行星，都服从牛顿力学或经典力学。另一方面，微观物体，如电子、原子和分子，遵守一套不同的规则，表现出量子力学的行为。由铝和氧化铝层组成的隧道结是独特的，因为它们是宏观物体，但它们具有量子力学行为的某些宏观特征。通过将这样的隧道结耦合到半导体，我们可以控制这个量子系统所耦合的环境，这在以前的任何量子系统中都不可能实现。该项目的目标之一是在各种结构中实现对环境的控制，以研究与各种系统相关的基本量子过程。 隧道结也可以用来制造一种新的探测器，称为单电子晶体管（SET），它的电荷灵敏度是商业上可用的晶体管的百万倍。SET的这种极端电荷敏感性使得许多独特的和潜在的重要实验成为可能。特别是，我们将使用与SET的混合来研究一种新的物质状态的一些显着特性，称为分数量子霍尔液体。在这种新的状态下，新的粒子产生了，它们具有非常不寻常的性质。我们的研究将利用SET的极端电荷敏感性来研究这些新粒子的这些不寻常的性质，这一直是分数量子霍尔效应领域的一个长期挑战。这项研究将伴随着一个全国性的推广计划，全国各地的高中生将进行合作测量，以确定北磁极的位置。在这样一个全球范围内进行测量将提供一个有趣的和真正的科学经验，我们希望这将激发学生对科学的一般。

The project centers on hybrid systems of Al/AlOx/Al tunnel junctions coupled with semiconductor heterostructures. Arrays of Al/AlOx/Al tunnel junctions are known to form a system with macroscopic degrees of freedom that behave quantum mechanically. By fabricating such a system of tunnel junctions on a GaAs/AlGaAs heterostructure with an electron gas located near the top surface of the heterostructure, we can directly control the dissipation independently of other parameters, something not previously possible in any quantum system. One of the goals of this project is to implement this control over dissipation in various structures in order to study fundamental tunneling processes and quantum phase transitions. On the semiconductor side, the hybrids also make feasible many unique and potentially important experiments. In particular, we will use the hybrids to study two of the most basic aspects, the charge and the statistics, of the excitations of fractional quantum Hall liquids (FQHLs). Remarkably, the excitations of the FQHLs, also called Laughlin quasiparticles, are predicted to carry fractional charge and obey unusual fractional statistics different from that for fermions or bosons. Measurement of fractional statistics, which we hope to tackle using Al/AlOx/Al tunnel junctions, has been a longstanding challenge in the field of fractional quantum Hall effect. The research will be accompanied by a nationwide outreach program, in which high school students across the country will do collaborative measurements to determine the position of the North magnetic pole. Doing a measurement on such a global scale will provide an interesting and genuine scientific experience, which we hope will excite students about science in general.%%%Typically macroscopic objects, such as dust particles, billiard balls, and planets, obey Newtonian, or classical mechanics. Microscopic objects, such as electrons, atoms, and molecules, on the other hand, obey a different set of rules and behave quantum mechanically. Tunnel junctions composed of aluminum and aluminum oxide layers are unique, in that they are macroscopic objects, yet they have certain macroscopic features that behave quantum mechanically. By coupling such tunnel junctions to semiconductors, we can control the environment to which this quantum system is coupled to, something not previously possible in any quantum system. One of the goals of this project is to implement this control over the environment in various structures in order to study fundamental quantum processes that are relevant to a rich variety of systems. Tunnel junctions can also be used to make a new a kind of detector, known as a single electron transistor (SET), which are million times more charge sensitive than commercially available transistors. This extreme charge sensitivity of SETs makes feasible many unique and potentially important experiments. In particular, we will use the hybrids with SETs to study some of the remarkable properties of a new state of matter, known as a fractional quantum Hall liquid. New kinds particles arise in this new state matter with very unusual properties. Our research will take advantage of the extreme charge sensitivity of SETs to investigate these unusual properties of these new particles, which have been a longstanding challenge in the field of fractional quantum Hall effect. The research will be accompanied by a nationwide outreach program, in which high school students across the country will do collaborative measurements to determine the position of the North magnetic pole. Doing a measurement on such a global scale will provide an interesting and genuine scientific experience, which we hope will excite students about science in general.***