Quantum Coherence and Mesoscopic Physics

这个凝聚态物理项目涉及“介观”金属样品--即亚微米尺度的样品。这些材料可以表现出令人惊讶的行为，特别是在含有不同类型材料的混合样品中--普通金属、超导体和铁磁体。最近的理论预测挑战了我们对这些材料的理解；这与长期以来的观点相矛盾，即铁磁体不能在超过几纳米的距离内保持超导相关性。这个实验项目将检验这一预测和其他关于超导体/铁磁和超导体/正常金属界面上的电传输的预测。此外，实验将探索正常金属在无序和电子-电子相互作用都非常强的情况下的输运特性--这是一种理论上很难理解的机制。介观物理实验研究对培养下一代科学家具有重要作用。参与该项目的研究生获得用于半导体行业的现代纳米制造技术方面的专业知识，这对纳米科学的未来发展和应用也是至关重要的。学生们接受了工业、学术和政府职业的培训。当金属样品被制造成非常小的尺寸--在微米范围内--它们表现出许多在大样品中看不到的电学性质。一些新的性质在室温下是明显的，而另一些只有在低温下才被揭示，当电子在许多微米范围内保持量子力学的相位一致性时。对金属小样品的研究，被称为介观物理，是一门丰富的学科，使人们对固体物理的许多方面有了更深的理解。这个项目解决了当前介观物理中的几个问题，包括高度无序金属中电子-电子相互作用的作用，相互接触的铁磁金属和超导金属之间的复杂相互作用，以及远离平衡的超导/正常金属约瑟夫森结的异常行为。介观物理实验研究对培养下一代科学家具有重要作用。从事这些项目的研究生获得了微电子工业中使用的样品处理技术方面的专业知识。在这类工作中发展起来的物理原理和实验技术对纳米科学的未来发展和应用至关重要。这些学生和博士后研究人员都经过了良好的培训，可以在工业、学术界和政府部门从事职业。

This condensed matter physics project deals with "mesoscopic" metallic samples - i.e. samples with submicron dimensions. These material can display surprising behavior, particularly in hybrid samples containing different types of materials - normal metals, superconductors, and ferromagnets. Recent theoretical predictions challenge our understanding of these materials; contradicting the long-held view that ferromagnets can not sustain superconducting correlations over distances longer than a few nanometers. This experimental project will test that prediction and others concerning electrical transport across superconductor/ferromagnet and superconductor/normal metal interfaces. In addition, experiments will probe the transport properties of normal metals when both disorder and electron-electron interactions are very strong - a regime poorly understood theoretically. Experimental research in mesoscopic physics plays an important role in educating the next generation of scientists. Graduate students involved in this project acquire expertise in modern nanofabrication techniques used in the semiconductor industry, which are also crucial to the future development and applications of nanosciences. The students are trained for careers in industry, academia, and government.When metallic samples are fabricated with very small dimensions - in the range of a micrometer - they exhibit many electrical properties not observed in larger samples. Some of the novel properties are evident at room temperature, while others are revealed only at low temperature, when electrons preserve quantum-mechanical phase coherence over many micrometers. The study of small metallic samples, called "mesoscopic physics", is a rich discipline and has led to a deeper understanding of many aspects of solid-state physics. This project addresses several current problems in mesoscopic physics, including the role of electron-electron interactions in highly-disordered metals, the complex interplay between ferromagnetic and superconducting metals in contact with each other, and the unusual behavior of superconducting/normal metal Josephson junctions driven far from equilibrium. Experimental research in mesoscopic physics plays an important role in educating the next generation of scientists. Graduate students working on these projects acquire expertise in sample processing techniques used in the microelectronics industry. The physical principles and experimental techniques developed in this kind of work are crucial to the future development and applications of nanosciences. The students and post-doctoral researchers are well trained for careers in industry, academia, and government.