4d and 5d Transition Metal Oxides: A New Frontier of Materials with Exotic Phenomena

这一个人研究人员奖支持系统地努力阐明4d和5d过渡金属氧化物的潜在物理。这些系统是一类新的材料，其特征是不同自由度之间的强耦合和不同种类的有序共存。最近的发现揭示了4d电子型金红石酸盐(sr，Ca)(n+1)Ru(N)O(3n+1)和5d电子型金红石酸锶(n+1)Ir(N)O(3n+1)的有趣物理性质，为深入研究提供了强大的动力。这些层状材料表现出惊人的物理性质的维度依赖性和广泛的奇异现象，包括费米子-准粒子和非金属特性的共存，平面间隧道磁阻，巨磁电阻(CMR)，截然不同的CMR和磁化各向异性，p波超导，超磁，绝缘态的“反磁”等。这些现象反映了新的物理现象，正是这种新的物理需要深入研究。计划中的计划包括单晶生长(熔剂和浮区法)以及这些材料的热、电、磁和结构性能随温度、化学掺杂、磁场和压力的实验研究。参与研究的研究生将接受严格的培训，重点是材料开发、合成和表征。如今，我们的研究生教育特别需要这种培训，因为缺乏专门从事开发新材料和生长单晶的科学家，这已经阻碍了美国凝聚态物理的进步。这一个人研究人员奖支持一项系统的努力，以阐明4d和5d过渡金属氧化物的基本物理，这些氧化物大体上是一个未知领域，蕴含着无法通过我们传统理解解释的新物理现象。最近的发现显示了基于4d电子的金红酸盐和基于5d电子的铁酸盐有趣的物理性质，并为深入研究提供了强大的动力。这些层状材料表现出惊人的物理性质的维度依赖性和广泛的奇异现象，包括新的超导电性和不同种类的有序的共存，传统上认为它们相互排斥等。这些现象在很大程度上挑战了传统的智慧，反映了新的物理学，正是这种新的物理学需要深入研究。计划中的计划包括材料合成和这类材料的热、电、磁和结构性能随温度、化学取代、磁场和压力的函数的实验研究。参与研究的研究生将接受严格的培训，重点是材料开发、合成和表征。我们的研究生教育特别需要这种类型的培训，因为缺乏专门从事新材料开发和单晶生长的科学家已经阻碍了美国凝聚态物理的进步。

This individual investigator award supports a systematic effort to elucidate underlying physics of the 4d and 5d transition metal oxides. These systems are a new class of materials characterized by strong coupling between different degrees of freedom and the coexistence of different kinds of ordering. Recent discoveries show a glimpse of intriguing physical properties of 4d-electron based ruthenates (Sr,Ca)(n+1)Ru(n)O(3n+1) and 5d-electron based iridates Sr(n+1)Ir(n)O(3n+1), and provide strong motivation for a thorough investigation. These layered materials exhibit an astonishing dimensionality-dependence of physical properties and a wide array of exotic phenomena including coexistence of fermion-quasiparticle and nonmetallic characteristics, inter-plane tunneling magnetoresistance, colossal magnetoresistance (CMR), drastically different anisotropies of the CMR and magnetization, p-wave superconductivity, metamagnetism, "diamagnetism" in an insulating state, etc. These phenomena reflect new physics, and it is this new physics that needs to be thoroughly studied. The planned program includes single crystal growth (both flux and floating zone methods) and experimental studies of thermal, electronic, magnetic and structural properties of these materials as a function of temperature, chemical doping, magnetic field and pressure. Graduate students involved in the research will receive rigorous training with an emphasis on materials developments, synthesis, and characterizations. This type of training in our graduate education is particularly needed nowadays as the lack of scientists who specialize in both developing new materials and growing single crystals has already hindered advancements in condensed matter physics in the US. This individual investigator award supports a systematic effort to elucidate underlying physics of the 4d and 5d transition metal oxides, which are by and large an uncharted territory rich with novel physical phenomena that cannot be explained through our conventional understanding. Recent discoveries show a glimpse of intriguing physical properties of 4d-electron based ruthenates and 5d-electron based iridates, and provide strong motivation for a thorough investigation. These layered materials exhibit an astonishing dimensionality-dependence of physical properties and a wide array of exotic phenomena including novel superconductivity and the coexistence of different kinds of ordering, which are conventionally expected to exclude each other, etc. These phenomena largely defy conventional wisdom and reflect new physics, and it is this new physics that needs to be thoroughly studied. The planned program includes materials synthesis and experimental studies of thermal, electronic, magnetic and structural properties of this class of materials as a function of temperature, chemical substitution, magnetic field and pressure. Graduate students involved in the research will receive rigorous training with an emphasis on materials developments, synthesis, and characterizations. This type of training in our graduate education is particularly needed nowadays as the lack of scientists who specialize in both developing new materials and growing single crystals has already hindered advancements in condensed matter physics in the United States.