Topics in Quantum Magnetism, Nanoelectronics and Superconductivity

该奖项支持凝聚态物理学的理论研究和教育，主要集中在三个相关领域：量子磁性、纳米电子学和超导性。尽管磁性的经典观点通常是成功的，但它在某些情况下是严重失败的，特别是在准一维（1D）系统中，原子自旋在晶体链上的相互作用比在链之间的相互作用强得多。从经典观点来看，在零温度下，原子自旋将沿固定方向排列（“上”和“下”）。这在低维系统中通常不会发生。相反，出现了强量子力学基态，其中自旋处于上下的集体线性叠加态。近年来，这已成为一个非常活跃的实验领域，通过日益完善的技术，合成和研究了许多准一维反铁磁体的例子。这部分是由于这些材料之间的联系，以及其中发生的一些现象，高温超导性和自旋电子学。PI将继续发展基本理论和有用的现象学，以理解目前各种准一维和准二维磁绝缘体的实验。随着电子元件的不断小型化，存储器元件、晶体管等的经典观点将面临极限，量子力学将发挥至关重要的作用。特别是，最近在“单电子晶体管”或量子点中观察到显著的量子现象，其中点上的电子数量可以在单个步骤中改变。这种纳米工程装置可以表现出先前在掺杂到金属中的原子杂质中研究过的行为，其中量子点扮演单个原子自旋的角色。这种自旋被来自金属的电子（或连接到量子点的引线）“屏蔽”。有人声称，这个筛选电子按顺序分布在一个很大的距离上。1 - 1微米。这种大长度尺度从未在实验中得到验证，并且一直是理论混乱的根源。量子点提供了独特的机会，最终观察到这个近藤筛选云。PI将发展对这种筛选云的理论理解，并旨在提出现实的设备和实验，从而可以测量它。高温超导体带来了重要技术应用的希望，同时也提出了非常困难的基础科学问题。本文将讨论这一领域的几个理论问题。特别是，通过与大规模数值模拟专家合作，他打算研究在某些材料（以及用于研究它们的某些模型）中，空洞将自己排列成由绝缘反铁磁区域隔开的窄“条纹”的可能性。这种情况如何普遍发生，原因是什么，以及它是否阻碍或帮助超导性是该领域的重要开放性问题。该奖项支持凝聚态物理学的理论研究和教育，主要集中在三个相关领域：量子磁学、纳米电子学和超导。尽管磁性的经典观点通常是成功的，但它在某些情况下是严重失败的，特别是在准一维（1D）系统中，原子自旋在晶体链上的相互作用比在链之间的相互作用强得多。从经典的观点来看，在零温度下，原子自旋会沿着固定的方向排列（比如“上”和“下”）。这在低维系统中通常不会发生。相反，出现了强量子力学基态，其中自旋处于上下的集体线性叠加态。近年来，这已成为一个非常活跃的实验领域，通过日益完善的技术，合成和研究了许多准一维反铁磁体的例子。这部分是由于这些材料之间的联系，以及其中发生的一些现象，高温超导性和自旋电子学。PI将继续发展基本理论和有用的现象学，以理解目前各种准一维和准二维磁绝缘体的实验。随着电子元件的不断小型化，存储器元件、晶体管等的经典观点将面临极限，量子力学将发挥至关重要的作用。特别是，最近在“单电子晶体管”或量子点中观察到显著的量子现象，其中点上的电子数量可以在单个步骤中改变。这种纳米工程装置可以表现出先前在掺杂到金属中的原子杂质中研究过的行为，其中量子点扮演单个原子自旋的角色。这种自旋被来自金属的电子（或连接到量子点的引线）“屏蔽”。有人声称，这个筛选电子按顺序分布在一个很大的距离上。1 - 1微米。这种大长度尺度从未在实验中得到验证，并且一直是理论混乱的根源。量子点提供了独特的机会，最终观察到这个近藤筛选云。PI将发展对这种筛选云的理论理解，并旨在提出现实的设备和实验，从而可以测量它。高温超导体带来了重要技术应用的希望，同时也提出了非常困难的基础科学问题。本文将讨论这一领域的几个理论问题。特别是，通过与大规模数值模拟专家合作，他打算研究在某些材料（以及用于研究它们的某些模型）中，空洞将自己排列成由绝缘反铁磁区域隔开的窄“条纹”的可能性。这种情况如何普遍发生，原因是什么，以及它是否阻碍或帮助超导性是该领域的重要开放性问题

This award supports theoretical research and education in condensed matter physics centered on three related areas: quantum magnetism, nanoelectronics and superconductivity.Although a classical view of magnetism is often successful, it fails badly in certain cases, in particular for quasi-one-dimensional (1D) systems where the atomic spins interact much more strongly along chains in a crystal than between chains. From a classical viewpoint, at zero temperature the atomic spins would align in fixed directions ("up "and "down "). This often doesn't occur in low dimensional systems. Instead, strongly quantum mechanical groundstates occur, in which the spins are in collective linear superpositions of up and down. In recent years this has become a very active experimental field, with numerous examples of quasi-one-dimensional antiferromagnets being synthesized and studied by increasingly refined techniques. This is motivated in part by the connection of these materials, and some of the phenomena that occur in them, with high-temperature superconductivity and spintronics. The PI will continue developing fundamental theory and useful phenomenology for understanding current experiments on various quasi-one-dimensional and quasi-two-dimensional magnetic insulators.As electronic components continue to miniaturize, a limit approaches where the largely classical views of memory elements, transistors, etc. break down and quantum mechanics plays a crucial role. In particular, remarkable quantum phenomena have been recently observed in "single electron transistors "or quantum dots, where the number of electrons on the dot can be varied in single steps. Such nano-engineered devices can exhibit behavior previously studied in atomic impurities doped into metals, with the quantum dot playing the role of a single atomic spin. Such a spin gets "screened " by an electron from the metal (or the leads connected to the quantum dot). It has been claimed that this screening electron is spread out over a very large distance, of order .1-1 microns. This large length scale has never been verified experimentally and has been a source of theoretical confusion. Quantum dots provide unique opportunities to finally observe this Kondo screening cloud. The PI will develop a theoretical understanding of this screening cloud and aims to propose realistic devices and experiments whereby it could be measured.The high-temperature superconductors hold out the promise of important technological applications and, at the same time, raise very difficult fundamental science issues. The will address several theoretical issues in this field. In particular, by collaborating with experts on large scale numerical simulations, he intends to study the possibility of holes arranging themselves into narrow "stripes "separated y insulating antiferromagnetic regions in some of these materials (and in some models used to study them). How generally this occurs, for what reasons and whether it hinders or helps superconductivity are important open questions in the field.%%%This award supports theoretical research and education in condensed matter physics centered on three related areas: quantum magnetism, nanoelectronics and superconductivity.Although a classical view of magnetism is often successful, it fails badly in certain cases, in particular for quasi-one-dimensional (1D) systems where the atomic spins interact much more strongly along chains in a crystal than between chains. From a classical viewpoint, at zero temperature the atomic spins would align in fixed directions (say, "up "and "down "). This often doesn't occur in low dimensional systems. Instead, strongly quantum mechanical groundstates occur, in which the spins are in collective linear superpositions of up and down. In recent years this has become a very active experimental field, with numerous examples of quasi-one-dimensional antiferromagnets being synthesized and studied by increasingly refined techniques. This is motivated in part by the connection of these materials, and some of the phenomena that occur in them, with high-temperature superconductivity and spintronics. The PI will continue developing fundamental theory and useful phenomenology for understanding current experiments on various quasi-one-dimensional and quasi-two-dimensional magnetic insulators.As electronic components continue to miniaturize, a limit approaches where the largely classical views of memory elements, transistors, etc. break down and quantum mechanics plays a crucial role. In particular, remarkable quantum phenomena have been recently observed in "single electron transistors "or quantum dots, where the number of electrons on the dot can be varied in single steps. Such nano-engineered devices can exhibit behavior previously studied in atomic impurities doped into metals, with the quantum dot playing the role of a single atomic spin. Such a spin gets "screened " by an electron from the metal (or the leads connected to the quantum dot). It has been claimed that this screening electron is spread out over a very large distance, of order .1-1 microns. This large length scale has never been verified experimentally and has been a source of theoretical confusion. Quantum dots provide unique opportunities to finally observe this Kondo screening cloud. The PI will develop a theoretical understanding of this screening cloud and aims to propose realistic devices and experiments whereby it could be measured.The high-temperature superconductors hold out the promise of important technological applications and, at the same time, raise very difficult fundamental science issues. The will address several theoretical issues in this field. In particular, by collaborating with experts on large scale numerical simulations, he intends to study the possibility of holes arranging themselves into narrow "stripes "separated by insulating antiferromagnetic regions in some of these materials (and in some models used to study them). How generally this occurs, for what reasons and whether it hinders or helps superconductivity are important open questions in the field.***