Transport and Magnetic Properties of NS Structures

NS 结构的输运和磁性

• 批准号: 9801982
• 负责人: Venkat Chandrasekhar
• 金额: $ 22.3万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2002-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9801982&HistoricalAwards=false
• 关键词: Transport; Magnetic; Properties; NS; Structures

9801982 Chandrasekhar This experimental condensed matter physics project addresses the fabrication and characterization of normal metal (N) - superconductors (S) structures whose dimensions are comparable to the fundamental coherence lengths in such materials. The electrical conductance and other properties of these nanostructures are predicted, and observed, to display non-classical and surprising behavior. This experimental project will extend our knowledge of the superconducting proximity effect by conducting the first measurements of the thermoelectric and magnetic response of NS structures. In the first part of the project, the energy and length dependence of the electrical conductance of normal wires in contact with a superconductor will be investigated in order to verify fundamental predictions of the theory of NS devices. The second part of the project is devoted to measuring the thermopower of so-called Andreev interferometers, which are loops in which one arm is fabricated from a superconductor and the other from a normal metal. In the last part of the project, the magnetic response of isolated Andreev interferometers will be measured using dc SQUID magnetometers. These last two properties have not been extensively studied, and their measurement should further our understanding of the correlations induced in the normal metal by its proximity to a superconductor. The samples for these experiments will be patterned and fabricated using electron-beam lithography. Their low temperature transport properties will be investigated by linear and nonlinear multiprobe differential resistance measurements as a function of temperature and magnetic field. The low temperature magnetic properties will be measured using ultra-sensitive dc SQUID magnetometers. Post-doctoral associates and graduate students trained on this project will be exposed to a wide variety of experimen tal techniques which will be useful in future careers in either industry or academia. %%% This experimental condensed matter physics project addresses the fabrication and characterization of ultra-small normal metal (N) - superconductors (S) structures. Superconductors have unusual electrical and magnetic properties at low temperatures, the best known being their ability to carry an electrical current without resistance. These properties form the basis for a number of practical devices such as very high field magnets. When a superconductor is placed in good contact with a conventional normal metal such as copper or gold, some of the superconducting properties "leak" a very small distance into the normal metal. With modern lithographic techniques borrowed from the semiconductor industry, it is now possible to probe the properties of normal metals on these very small size scales. The aim of this project is to investigate the electrical, thermoelectric and magnetic properties of such small normal metals placed in close proximity to a superconductor. In the first part of this project, the electrical properties of normal metal wires in proximity to a superconductor will be studied to verify and further our current theoretical understanding of the nature of the superconductivity induced in the normal metal. In the second and third parts of the project, the consequences of this induced superconductivity on the thermoelectric and magnetic properties of the normal metal wires will be explored. These last two properties have not been yet been studied experimentally, and these measurements will help us gain further insight into the interaction between superconductors and normal metals on very small size scales. The samples for these experiments will be fabricated using advanced electron-beam lithography techniques, and measured using sophisticated resistance and magnetic sensors a t temperatures near absolute zero. Post-doctoral associates and graduate students trained on this project will be exposed to a number of experimental techniques which will be useful in future careers in either industry or academia. ***

9801982 Chandrasekhar这个实验性冷凝物理物理项目介绍了正常金属（N） - 超导体（S）结构的制造和表征，其尺寸与此类材料中的基本相干长度相媲美。预测并观察到这些纳米结构的电导和其他特性，以表现出非古典和令人惊讶的行为。 这个实验项目将通过进行NS结构的热电和磁反应的首次测量来扩展我们对超导接近效应的了解。在项目的第一部分中，将研究与超导体接触的正常电线的能量和长度依赖性，以验证NS设备理论的基本预测。 该项目的第二部分致力于测量所谓的Andreev干涉仪的热电器，该仪是一个循环，其中一个臂是用超导体制造的，另一只手臂是由普通金属制成的。 在项目的最后一部分中，将使用DC Squid磁力计测量分离的Andreev干涉仪的磁反应。 这些最后两个属性尚未进行广泛的研究，它们的测量应进一步了解正常金属与超导体的近距离所引起的相关性。 这些实验的样品将使用电子束光刻进行图案化和制造。它们的低温传输性能将通过线性和非线性多杆差异电阻测量作为温度和磁场的函数研究。 低温磁性特性将使用超敏感的直流鱿鱼磁力计测量。接受该项目的培训的博士后伙伴和研究生将接触到各种各样的实验性TAL技术，这些技术将在行业或学术界的未来职业中有用。 %% %%这个实验性凝分物理项目项目解决了超小型正常金属（N） - 超导体（S）结构的制造和表征。超导体在低温下具有异常的电气和磁性，最著名的是它们携带无电流的电流的能力。 这些属性构成了许多实用设备，例如非常高的场磁体。当将超导体与常规金属（例如铜或金）保持良好接触时，某些超导特性“泄漏”了与正常金属的距离很小的距离。 借助从半导体行业借来的现代光刻技术，现在可以在这些尺寸很小的尺度上探测普通金属的性质。该项目的目的是研究如此小的正常金属的电气，热电和磁性，与超导体紧密相近。 在该项目的第一部分中，将研究正常金属线与超导体接近的电气特性，以验证并进一步我们当前对正常金属诱导的超导性质的理论理解。在项目的第二部分和第三部分中，将探索这种诱导的超导性对正常金属电线的热电和磁性特性的后果。这些最后两种属性尚未进行实验研究，这些测量将有助于我们进一步了解超导体和正常金属之间的相互作用，这是很小的尺寸尺度。 这些实验的样品将使用先进的电子束光刻技术制造，并使用复杂的电阻和磁性传感器的t温度接近绝对零。 接受该项目的培训的博士后伙伴和研究生将接触到许多实验技术，这些技术将在行业或学术界的未来职业中有用。 ***