Quantum Coherent Phenomena in Superconducting Heterostructures

超导异质结构中的量子相干现象

• 批准号: 1006445
• 负责人: Venkat Chandrasekhar
• 金额: $ 48万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006445&HistoricalAwards=false
• 关键词: Quantum; Coherent; Phenomena; Superconducting; Heterostructures

****NON-TECHNICAL ABSTRACT****According to quantum mechanics, small objects such as electrons behave like waves in addition to behaving like discrete particles. As waves, electrons show many interesting effects. An example is the interference of waves: think of the patterns of waves on the surface of a small pond when a stone is thrown in it. Quantum waves also encode the results of various interactions and correlations between particles, and devices that take advantage of these effects are the fundamental building blocks of many modern electronic devices. The effects of interference and correlations between electrons due to their wave nature can be seen by measuring the electric currents that are generated by them. However, these fragile interference and correlation effects are easily destroyed, and extremely low temperatures (close to absolute zero) and very sensitive measurement techniques are required to observe them. This project will explore correlations between electrons in metals that are induced by their interactions with a superconductor, which is a material that can carry an electrical current without resistance at very low temperatures. The experimental techniques that will be used include fabrication of very small devices that include metallic and superconducting parts, and measurements of the currents and voltages through these devices, as well as the electrical noise generated by these currents and voltages at very low temperatures. A major component of this project is the involvement of undergraduate and graduate students in research, who will learn sophisticated techniques of nanofabrication and device measurements. This training will enable the students to have careers in academia or high-technology industries.****TECHNICAL ABSTRACT****This project will explore quantum correlations induced in normal metals and ferromagnets due to their interactions with superconductors. In particular, the primary focus of this project will be on non-local correlations introduced in spatially separated normal metals and ferromagnets induced by crossed Andreev reflection (CAR) and elastic co-tunneling (EC). CAR and EC will be probed using nonlocal electrical transport measurements as well as noise measurements. The noise measurements will also be used to probe for spin entanglement of quasiparticles using samples with ferromagnetic elements. A second set of measurements will focus on the conditions under which one can observe superconducting correlations over long length scales in systems with finite spin polarization. While superconducting correlations have been observed in ferromagnets, the length scale over which these correlations extend has been extremely short. The new material systems that will be investigated may extend this length scale, and lead to the possibility of new superconducting devices in addition to furthering our understanding of exotic forms of superconductivity in ferromagnets. Integral to the project is the training of graduate and undergraduate students in nanofabrication and sophisticated measurement techniques.

****非技术抽象****根据量子力学，除了像离散粒子一样行为外，诸如电子之类的小物体（例如电子）表现得像波浪一样。 随着波浪，电子显示许多有趣的效果。 一个例子是波浪的干扰：当将一块石头扔进其中时，想想小池塘表面上的波浪模式。 量子波还编码了粒子之间各种相互作用和相关性的结果，利用这些效果的设备是许多现代电子设备的基本构建块。 通过测量其产生的电流，可以看到干扰性和电子之间的干扰和相关性的影响。 但是，这些脆弱的干扰和相关效应很容易被破坏，并且需要极低的温度（接近绝对零），并且需要非常敏感的测量技术才能观察它们。 该项目将探索金属中电子与超导体相互作用引起的电子之间的相关性，该材料可以在非常低的温度下携带电流而不会电流。 将使用的实验技术包括制造非常小的设备，包括金属和超导零件，以及通过这些设备的电流和电压的测量，以及这些电流和电压在非常低温下产生的电噪声。 该项目的主要组成部分是研究生和研究生参与研究，他们将学习纳米制作和设备测量的复杂技术。 这项培训将使学生能够从事学术界或高科技行业的职业。 特别是，该项目的主要重点将放在通过空间分离的正常金属和由Andreev Reflection（CAR）和弹性共同调节（EC）引起的非本地相关性。 CAR和EC将使用非局部电气传输测量以及噪声测量进行探测。 噪声测量值也将用于使用具有铁磁元件的样品探测清单的自旋纠缠。 第二组测量值将集中在有限自旋极化系统中长长尺度上可以观察到超导相关性的条件。 尽管已经在铁磁体中观察到超导相关性，但这些相关性扩展的长度尺度非常短。 将要研究的新材料系统可能会延长这一长度规模，并可能导致新的超导设备除了进一步了解我们对铁磁性超导性外在形式的理解。 该项目不可或缺的是培训纳米制作和复杂测量技术的研究生和本科生。