Quantum Critical Phenomena in Disordered Interacting Bose Systems

无序相互作用玻色系统中的量子临界现象

• 批准号: 9206023
• 负责人: Richard Scalettar
• 金额: $ 23.38万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-01 至 1995-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9206023&HistoricalAwards=false
• 关键词: Quantum; Critical; Phenomena; Disordered; Interacting

The physics of disordered, correlated Bose sytems constitutes a major challenge. Recently a density controlled superfluid transition was observed in helium-four absorbed in porous materials with a superfluid density exponent contrdicting earlier theories; new types of scaling behavior of the resistivity have been seen in disordered superconducting films and wires; and the observation of a possible universal conductance in granular superconducting films has attracted considerable excitement. A related problem of primary importance is the vortex state of the high temperature superconductors, where an unconventional, vortex-glass phase has been observed in some materials. At the same time, the discovery of heavy fermion and oxide superconductors has driven a substantial improvement in numerical techniques and also led to genuinely new analytical approaches to strongly correlated fermions. These advanceshave yet to be applied to the interacting boson problem. The research will apply Quantum Monte Carlo, the Schwinger boson approach and the perturbative scaling methids of localization theory to explore the quantum phase transitions taking place in helium-four absorbed in porous media and granular superconductors, as modeled by a disordered, interacting boson Hamiltonian. The disorder will be handled by methods which were successful in the spin-glass problem, among others finite size scaling of appropriately chosen dimensionless quantities, and a suitable version of the maximum entropy method. %%% Theoretical research will be conducted using numerical and analytical techniques to study the behavior of disordered, interacting many particle systems which obey Bose statistics. New methods will be applied to describe such diverse physical systems as properties of helium absorbed in porous materials and the behavior of high temperature superconductors.

无序、相关的 Bose 系统的物理学构成了一项重大挑战。 最近，在吸附在多孔材料中的氦四中观察到密度控制的超流体转变，其超流体密度指数与早期理论相矛盾； 在无序超导薄膜和导线中发现了新型电阻率缩放行为；在粒状超导薄膜中观察到可能存在的普遍电导引起了相当大的兴奋。 一个最重要的相关问题是高温超导体的涡旋态，在一些材料中观察到非常规的涡旋玻璃相。 与此同时，重费米子和氧化物超导体的发现推动了数值技术的实质性改进，也带来了强相关费米子的真正新的分析方法。 这些进展尚未应用于相互作用的玻色子问题。 该研究将应用量子蒙特卡罗、施温格玻色子方法和局域化理论的微扰标度方法来探索吸收在多孔介质和粒状超导体中的氦四中发生的量子相变，如无序相互作用的玻色子哈密顿量所建模的。 这种无序将通过在自旋玻璃问题中成功的方法来处理，其中包括适当选择的无量纲量的有限尺寸缩放，以及最大熵方法的合适版本。 %%% 理论研究将使用数值和分析技术来研究服从玻色统计的无序、相互作用的许多粒子系统的行为。 新方法将用于描述多孔材料中吸收的氦的特性和高温超导体的行为等不同的物理系统。