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

w：\awards\awards96\*.doc 9631236 Cohn 本研究对掺杂类钙钛矿结构过渡金属氧化物的晶格和电子输运进行了系统的实验研究。 这些研究的目标是阐明和模拟晶格振动在确定 超导和磁相行为 这些材料，特别是铜和锰的氧化物。 热导率和热电势将被用作晶格与电荷和自旋自由度之间相互作用的探针。 这些相互作用与电荷载流子掺杂的演变及其对温度和磁场的依赖性是本研究的中心焦点。 在这些研究中，选择具有类似晶体结构但具有铜和锰以外的过渡金属的抗氧化剂系统作为“对照”。这些包括钌和镍的氧化物的化合物，其电子-晶格和电子-电子相互作用的强度似乎非常不同。 本研究的重点是过渡金属氧化物中的电子和热传导物理，这是一种广泛的材料，近年来引起了相当大的关注，因为它们的特性表现出新颖的物理特性，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相互作用，分别控制在铜和锰氧化物的超导和磁相变。 这些转变在每一类材料中以系统的方式随电荷载流子浓度而变化。 这些相行为的机制的签名将寻求在温度和磁场的依赖性的热输运性质，其中一些异常已经被确定。 ***

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. ***