Thermal Transport in Copper and Manganese Oxides: Lattice Interactions and the Superconducting and Magnetic Phase Behavior

这项研究涉及到钙钛矿型结构掺杂过渡金属氧化物中晶格和电子输运的系统实验研究。这些研究的目标是阐明晶格振动在确定这些材料，特别是铜和锰氧化物中的超导和磁相行为方面的作用并建立模型。热导率和热电势将被用来探测晶格与电荷和自旋自由度之间的相互作用。这些相互作用随载流子掺杂的演化以及它们对温度和磁场的依赖是本研究的中心焦点。在这些研究中，具有相似晶体结构、但含有铜和锰以外的过渡金属的模拟体系被选为“对照”。其中包括电子-晶格和电子-电子相互作用强度似乎非常不同的Ru和镍氧化物化合物%这项研究集中在过渡金属氧化物中的电子和热传导物理，这是近年来引起人们极大关注的一大类材料，因为它们的性质表现出新的物理特性，以及它们在未来技术中的潜在用途。在这项研究中特别感兴趣的是分别控制铜和锰氧化物中超导相变和磁性相变的相互作用。在每一类材料中，这些转变随载流子浓度的不同而有系统地变化。这些相行为背后的机制的签名将在热传输性质的温度和磁场相关性中寻找，其中一些异常已经被识别。***

w:\awards\awards96\*.doc 9631236 Cohn This research involves systematic experimental studies of lattice and electronic transport in doped transition metal oxides of perovskite-like structure. The goal of these studies is to elucidate and model the role of lattice vibrations in determining the superconducting and magnetic phase behavior in these materials, particularly in the copper and manganese oxides. Thermal conductivity and thermopower will be employed as probes of interactions between the lattice and the charge and spin degrees of freedom. The evolution of these interactions with charge-carrier doping and their dependence on temperature and magnetic field are a central focus of this research. Analogue systems with similar crystal structure, but with transition metals other than copper and manganese, have been selected as "controls" in these studies. These include ruthenium and nickel oxide compounds for which the strength of electron-lattice and electron-electron interactions appear to be very different %%% This research focuses on the physics of electronic and thermal conduction in transition metal oxides, a broad class of materials that have attracted considerable attention in recent years both for the novel physics their properties manifest, and for their potential use in future technologies. Of particular interest in this study are the interactions which control the superconducting and magnetic phase transitions in the copper and manganese oxides, respectively. These transitions vary with charge-carrier concentration in systematic ways within each class of materials. Signatures of the mechanisms underlying these phase behaviors will be sought in the temperature and magnetic field dependencies of the thermal transport properties, where some anomalies have already been identified. ***