Metals, Insulators, and Superconductors

将发展金属、绝缘体和超导体的电子和振动性质的理论，特别是晶态氧化物，如铜和铋氧化物超导体和钒-氧化物基金属-绝缘体系统。潜在的动机是探索高温超导仍不清楚的机制。这项研究的次要动机是提高对这些材料多样且知之甚少的电传输特性的了解。作为一个模型系统，我们将详细研究钡铋氧化物。这种绝缘体中的载流子是双极化子。当铋被铅取代时，从奇异的超导态到正常的金属导体的不断演变发生。将开发和测试极化子和双极化子模型来模拟电阻率、霍尔系数和超导电性。其他要研究的模型体系是氧化Nb和二氧化钒。后者在便于存储元件等器件应用的温度下具有金属-绝缘体转变。我们将研究晶格扭曲和声子对相变的影响。还将在非晶硅的模型中研究热传导。

Theory will be developed for the electronic and vibrational properties of metals, insulators and superconductors, especially crystalline oxides such as copper-and bismuth-oxide superconductors and vanadium-oxide based metal-insulator systems. The underlying motive is to explore the still obscure mechanism for high temperature superconductivity. A secondary motive for the research is to improve understanding of the diverse and poorly understood electrical transport properties of these materials. As a model system barium-bismuth-oxide will be studied in detail. The charge carriers in this insulator are bipolarons. A continuous evolution through an exotic superconducting state to a normal metallic conductor occurs as bismuth is replaced by lead. Polaron and bipolaron models will be developed and tested to model resistivity, Hall coefficient, and superconductivity. Other model systems to be studied are niobium-oxide and vanadium-dioxide. The latter has a metal-insulator transition at a temperature convenient for device applications such as memory elements. The effect of lattice distortion and phonons on the transition will be studied. Thermal conduction will also be studied in a model of amorphous silicon.