Counterflow Superfluidity and Tunnelling in Quantum Hall Bilayers

量子霍尔双层中的逆流超流性和隧道效应

• 批准号: EP/C546814/1
• 负责人: Derek Lee
• 金额: $ 20.67万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FC546814%2F1
• 关键词: Counterflow; Superfluidity; Tunnelling; Quantum; Hall

Electrons are the charged particles that are responsible for the conduction of electricity in everyday materials, such as copper wires and the silicon chips in a PC. In the last decade, researchers have discovered that, if we squeeze the electrons into flat sheets which are just a millionth of a centimetre in thickness, they appear to behave quite differently from what we expect.The most dramatic examples of electrons in flatland are the high-temperature superconductors where the electrons live on copper-oxide planes. The electrons appear to flow without experiencing any resistance. This means that electric currents can flow in these materials without losing energy as heat. If we can persuade these materials to behave like this at room temperature, there will be the basis for a whole variety of exciting new technologies.This project looks at another flatland system which displays equally bizarre effects, recently seen by researchers in Bell Labs and Princeton. In a tour de force of experimental techniques, they have managed to fabricate two parallel flat sheets of electrons very close together with leads attached independently to each sheet. They then placed their sample in a strong magnetic field (a million times the strength of the Earth's magnetic field). In this bilayer , they see something which looks very much like superconductivity, when they cause currents to flow in opposite directions in the two electron sheets! In other words, the counterflowing currents can flow without resistance. They have called this effect counterflow superfluidity .Theorists suspect that this phenomenon is intimately connected to the fact that electrons in flatland are particularly sensitive to the repulsive forces that exist between them. In this case, the repulsion between electrons in different sheets is as strong as the repulsion between electrons in the same sheet. So, the motion of electrons in the top layer causes electrons in the bottom layer to move away in the opposite direction.This project is designed to explore this theoretical picture of counterflow superfluidity. Many theories have been put forward, but they cannot explain some very prominent features in the experimental data. Indeed, no one can explain why the counterflow can occur over the whole sample. Why do the electrons go all the way from one side of the sample to the other on the top layer, only to come back in the other direction on the bottom layer -- they could have jumped over halfway along!We want to provide a microscopic theory that can explain the puzzles from the experiments. Only when these puzzles are resolved can we be confident that this phenomenon of counterflow superfluidity exists. From a wider perspective, we hope that the theory that we develop for this problem will shed some light on how to understand the intriguing games that electrons play in flatland .

电子是负责日常材料中导电的带电粒子，例如铜线和个人电脑中的硅片。在过去的十年里，研究人员发现，如果我们把电子压缩到只有百万分之一厘米厚的平板上，它们的行为似乎与我们预期的完全不同。平面上电子最引人注目的例子是高温超导体，电子生活在氧化铜平面上。电子似乎在没有任何阻力的情况下流动。这意味着电流可以在这些材料中流动而不会以热量的形式损失能量。如果我们能让这些材料在室温下表现得像这样，那么一系列令人兴奋的新技术就有了基础。最近，贝尔实验室和普林斯顿大学的研究人员发现了另一种表现出同样奇怪效果的平地系统。在实验技术的力作中，他们成功地制造了两个平行的扁平电子片，它们非常紧密地连接在一起，每片电子片上都有独立的引线。然后他们把样本放在一个强磁场中（比地球磁场强100万倍）。在这个双层中，他们看到了一些看起来很像超导的东西，当它们在两个电子片中引起电流朝相反方向流动时！换句话说，逆流的电流可以无阻力地流动。他们称这种效应为逆流超流。理论学家怀疑，这种现象与平面上的电子对它们之间存在的排斥力特别敏感这一事实密切相关。在这种情况下，不同薄片中电子之间的排斥力与同一薄片中电子之间的排斥力一样强。所以，顶层电子的运动导致底层电子向相反方向移动。本项目旨在探索逆流超流动性的理论图景。人们提出了许多理论，但它们都不能解释实验数据中一些非常突出的特征。事实上，没有人能解释为什么逆流会发生在整个样本上。为什么电子会从样品的一边到顶层的另一边，然后又从另一个方向回到底层——它们可能在中途跳过！我们想提供一种微观理论来解释实验中的困惑。只有解决了这些难题，我们才能确信这种逆流超流体现象的存在。从更广泛的角度来看，我们希望我们为这个问题开发的理论将有助于理解电子在平面上的有趣游戏。

项目成果

Breakdown of Counterflow Superfluidity in a Disordered Quantum Hall Bilayer

无序量子霍尔双层中逆流超流的分解

• DOI: 10.1155/2011/792125
• 发表时间: 2011
• 期刊: Advances in Condensed Matter Physics
• 影响因子: 1.5
• 作者: Lee D

Feshbach resonant scattering of three fermions in one-dimensional wells

一维井中三个费米子的 Feshbach 共振散射

• DOI: 10.1103/physreva.80.033611
• 发表时间: 2009
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Ðuric T