Low - Dimensional Transition Metal Oxides with Correlated Electronic Properties: Synthesis and Characterization

由固态和材料化学计划支持的实验计划的重点是合成具有强相关电子性质的新材料，这些材料处于电子和结构不稳定性的边缘，并以受控的方式通过不稳定区域微调竞争电子相互作用。经验表明，当存在竞争性电子相互作用时，可能会发现具有新颖行为的材料。在低维（LD）材料中，竞争电子相互作用的相互作用增强。本项目的目标是合成和表征具有准LD特性的新型还原/氧化过渡金属化合物。将研究许多系统，这些系统共享局部和巡回自由度之间相互作用的共同特征，高度可变的传导电子带宽，其可以通过改变例如，晶体结构、化学成分、外加应力和无序度。带宽的可变性导致了各种重要的现象，包括由温度、压力、磁场、电场、照明、晶格畸变和其他变量的变化驱动的金属-绝缘体转变（或尖锐的交叉）。我们预计，在这些转变附近的运输，电子/磁性也将发生显着变化，将是可调的。实验研究将通过密度泛函理论计算的电子结构的理论研究来增强。这些研究有望产生新的材料，提供相关的电子和磁性行为的基本见解，并最终允许增强和控制电子-声子和/或电子-电子相互作用以及并发的磁耦合，从而产生有趣和有用的宏观性质。非技术总结这项研究将为微电子和磁电子学的潜在应用提供先进的材料，包括计算机，传感器和通信。这些都是保持美国全球技术领先地位的关键领域。此外，固态化学/材料科学的本科生、研究生和博士后研究员的教育和培训对于迎接二十一世纪的技术挑战至关重要。这项研究是高度跨学科的。PI与其他化学家，物理学家和陶瓷学家的合作工作在国内和国际上都得到了很好的建立。这项工作的单晶和其他材料产品提供给科学界进行详细的进一步调查。

TECHNICAL SUMMARYThe focus of the experimental program, supported by the Solid State and Materials Chemistry program is to synthesize new materials with strongly correlated electronic properties that are on the verge of electronic and structural instabilities, and to fine-tune the competing electronic interactions through the unstable region in a controlled way. Experience shows that materials with novel behavior are likely to be discovered when competing electronic interactions exist. In low-dimensional (LD) materials the interplay of competing electronic interactions is enhanced. The object of this project is the synthesis and characterization of new reduced/oxidized-transition metal compounds with quasi-LD properties. A number of systems will be investigated which share the common feature of interplay between localized and itinerant degrees of freedom, a highly variable conduction electron bandwidth, which may be tuned by changing e.g., the crystal structure, chemical composition, external strain and degree of disorder. The variability of bandwidth leads to a variety of important phenomena, including metal-insulator transitions (or sharp crossovers) driven by variation of temperature, pressure, magnetic field, electric field, illumination, lattice distortion and other variables. We expect that in the vicinity of these transitions the transport, electronic/magnetic properties will also change dramatically and will be tunable. The experimental studies will be augmented by theoretical investigation of the electronic structure by density functional theoretical calculations. These studies are expected to yield novel materials, provide fundamental insights into correlated electronic and magnetic behavior and ultimately allow the enhancement and control of electron-phonon and/or electron-electron interactions and the concurrent magnetic couplings that lead to interesting and useful macroscopic properties. NON-TECHNICAL SUMMARYThe research will provide advanced materials for potential applications in microelectronics and magneto-electronics, including computers, sensors and communications. These are critical areas for maintaining US technological leadership worldwide. Moreover, the education and training of undergraduate and graduate students and postdoctoral fellows in solid state chemistry/materials science is essential to meet the technological challenges of the twenty first century. The research proposed is highly interdisciplinary. Collaborative work of the PI with other chemists, physicists and ceramicists is well established nationally and internationally. Single crystals and other material products of the work are provided to the scientific community for detailed further investigations.