Magnetized States of Quantum Spin Chains

9801742 Reich这是一个实验研究计划，旨在描述准一维量子自旋系统的磁化态，以及与磁场相关的临界性质--诱导T=0相变到这种态。这项工作的目的是(I)确定自旋链的磁化态是否共享一个与理论预测的磁化强度成反比的无公度长度尺度，以及(Ii)为不断增长的关于量子临界现象的理论结果提供一个实验对应物。这项工作涉及到一系列详细的实验，在这些实验中，自旋哈密顿量可以通过施加磁场来重复地改变，并且可以以受控的方式引入无序。一些不同的准一维反铁磁体将被研究，包括具有自旋S=1/2和S=1的直线链，具有键交替的直线链，以及自旋梯形。这项研究涉及研究生和本科生，他们在实验凝聚态物理方面获得了广泛的教育，从样品制备到各种类型的实验和分析，再到结果的传播。这项研究的目标是通过对简单磁系统的详细实验研究，增加对多体量子物理基本行为的理解。量子自旋链是一种磁铁，其中原子尺度的磁相互作用只在材料的一个方向上很强。这种一维性与量子力学相结合，产生了具有新颖而美丽的特性的系统，在这些系统中，高度复杂的理论概念可以进行严格的实验测试。这项研究涉及研究生和本科生，他们在实验凝聚态物理方面获得了广泛的教育，从材料制备和各种尖端实验技术到复杂的数据分析和结果传播。***

9801742 Reich This is an experimental research program designed to characterize magnetized states of quasi--one--dimensional quantum spin systems, and the critical properties associated with the magnetic field--induced T = 0 phase--transitions into such states. The goals of this work are to (i) determine whether magnetized states of spin chains share an incommensurate length scale which is inversely proportional to magnetization as predicted by theory and (ii) to provide an experimental counterpart to the growing body of theoretical results about quantum critical phenomena. This work involves a series of detailed experiments on well- characterized model systems where the spin Hamiltonian can be varied reproducibly through the application of a magnetic field, and where disorder can be introduced in a controlled fashion. A number of different quasi-one-dimensional antiferromagnets will be investigated, including linear chains with spin S=1/2 and S=1, linear chains with bond alternation, and spin ladders. The research involves both graduate and undergraduate students who obtain a broad education in experimental condensed matter physics, from sample preparation through various types of experiments and analysis to the dissemination of results. %%% The goal of this research is to increase the understanding of the fundamental behavior of many-body quantum physics through detailed experimental studies of simple magnetic systems. Quantum spin chains are magnets in which the atomic-scale magnetic interactions are strong only in one direction in the material. This one-dimensionality coupled with quantum mechanics produces systems with novel and beautiful properties where highly sophisticated theoretical concepts can be put to rigorous experimental tests. The research involves both graduate and undergraduate students who obtain a broad education in experimental condensed matter physics, from materials pre paration and a variety of cutting-edge experimental techniques to sophisticated data analysis and the dissemination of results. ***