NMR Studies of the Competition Between Ground States in Correlated Electron Systems

这个项目涉及相关电子系统中竞争基态的物理研究。低温相的性质以及不同基态之间的相变有待确定。调节外部参数，如压强、无序度、化学计量比和磁场，将控制相变。具体地说，将研究反铁磁性与超导电性或有序自旋-Peierls相竞争的相变。此外，还将关注与有机超导体(TMTSF)2PF6以及锶和锂共掺的高T_c超导体铜酸镧的反铁磁性向超导电性演化有关的性质。我们将考察(TMTTF)2x系统中的自旋-Peierls/反铁磁相变，其中x=PF6或AsF6。主要的探头是核磁共振光谱学，在不同但受控的高压和强磁场条件下，以访问不同的相。首席调查员将与研究生和本科生合作进行这项研究。学生将参与实验的设计、计划和执行阶段。他们将学习当前研究领域的各种技术技能，从而接受培训，以便在21世纪今后几十年内在具有重要技术意义的领域就业。这个项目关注的是研究新材料如何在不同的物理状态下共存，以及这些状态之间的跃迁如何相互竞争。所讨论的材料是那些表现出例如超导和其他现象的材料，这些现象因其自身固有的科学兴趣以及在新技术设备中的潜在应用而受到广泛研究。研究生和本科生以及博士后研究助理参与了这项工作，因此接受了凝聚态物理和材料科学前沿领域的培训。因此，他们准备进入未来的科学/技术劳动力大军。

This project concerns the study of the physics of competing ground states in correlated electron systems. The properties of low temperature phases as well as the phase transition between different ground states are to be determined. Tuning external parameters, such as the pressure, disorder, stoichiometry and magnetic field will control the phase transitions. Specifically, phase transitions will be investigated in which antiferromagnetism competes with either superconductivity or an ordered Spin-Peierls phase. Additional attention will be given to the properties associated with the evolution from antiferromagnetism to superconductivity in the organic superconductor (TMTSF)2PF6, and the high-Tc superconductor lanthanum cuprate co-doped with Sr and Li. The Spin-Peierls/antiferromagnetic transition in the systems (TMTTF)2x, where x = PF6 or AsF6 will be examined. The primary probe is NMR spectroscopy, under varied but controlled conditions of high pressure and high magnetic fields in order to access the different phases. The Principal Investigator will conduct this research in collaboration with graduate and undergraduate students. The students will be involved in the design, planning and execution stages of the experiments. They will learn a variety of technical skills in areas of current research and are thereby trained for employment in fields of technological importance during the next few decades of the 21st Century. %%%This project is concerned with the investigation of how novel materials can coexist in different physical states and how transitions between these states compete with one another. The materials in question are those that exhibit, for example, superconductivity and other phenomena which are intensively studied for their own intrinsic scientific interest as well for their potential applications in new technological devices. Graduate and undergraduate students, as well as postdoctoral research associates participate in this work and are thereby trained in forefront areas of condensed matter physics and materials science. They are thus prepared to enter the scientific/technical workforce of the future.***