Quasi-One-Dimensional Correlated Electronic Materials

准一维相关电子材料为量子多体物理的发展提供了一个独特的机会。理论问题比较容易处理，比高维的问题好。可以发展数值和理论技术，并与实验进行比较，并经常与现有的精确解进行比较。这笔资助给一位资深理论家的资金将用于研究两类相关的一维物理模型，即自旋-佩尔斯模型和佩尔斯-哈伯德模型。这两类都涉及电子-电子相互作用和电子-声子相互作用之间的强相互作用，包括量子声子。该研究利用了许多最先进的技术，最近开发的量子蒙特卡罗的两种变体，随机级数展开和约束路径蒙特卡罗。此外，将使用精确对角化技术，利用最大熵技术进行分析延拓，并利用边界条件平均进行热力学极限外推。对自旋磁化率、动态结构因子、核磁共振弛豫率等物理观测值进行计算，并与实验结果进行比较。随着对导电聚合物的技术兴趣的出现，凝聚态理论学界发现了一个绝佳的机会。在这里，我们有复杂的系统，在一维中具有微妙的电子和机械特性。后者在数学上是寻找复杂解的最简单配置。它也被证明是一块非凡的试金石，可以测试复杂的理论技术的适用性和准确性。这项拨款是为了考虑一些新发现的具有新特性的材料，并寻找可以使用尖端技术在理论上计算它们的方法。＊＊＊

9712765 Campbell Quasi-one-dimensional correlated electronic materials offer a unique opportunity for progress in quantum many-body physics. The theoretical problems are tractable, better than in higher dimensions. The numerical and theoretical techniques can be developed and compared with experiments and often against available exact solutions. This grant to a senior theorist supports work on two related classes of physically relevant 1D models, spin -Peierls and Peierls- Hubbard models. Both classes involve strong interplay between electron-electron interactions and electron- phonon interactions, including the quantum phonons. The research makes use of many of the state-of-the-art techniques, two of the recently developed variants of quantum Monte Carlo, the Stochastic Series Expansion and Constrained Path Monte Carlo. In addition, use will be made of the exact diagonalization techniques, exploiting Maximum-Entropy techniques for analytic continuation and also boundary condition averaging for extrapolations to the thermodynamic limit. The calculations will be carried out for the physical observables such as, spin susceptibility, dynamic structure factors, NMR relaxation rates which will also be compared to the experiments. %%% With the advent of technological interest in conducting polymers, the community of condensed matter theorists has found a wonderful opportunity. Here we have complex systems with subtle electronic and mechanical properties in one dimension. The latter is mathematically the simplest configuration to look for complex solutions. It also proves to be a remarkable touchstone, one where the complex theoretical techniques can be tested for their applicability and accuracy. This grant is to consider some of the newly discovered materials with novel properties and to search for ways one can calculate them theoretically using cutting edge techniques. ***