Pressure Tuned Quantum Phase Transitions in Model Itinerant Magnets

模型流动磁体中的压力调节量子相变

• 批准号: 0907025
• 负责人: Thomas Rosenbaum
• 金额: $ 36.9万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907025&HistoricalAwards=false
• 关键词: Pressure; Tuned; Quantum; Phase; Transitions

Technical AbstractThere has been enormous activity devoted to quantum phase transitions in complicated and often disordered materials: rare earth cuprates, heavy fermion materials, transition metal oxides and sulfides Ideally, one would like to tune a simple, stoichiometric material to its quantum critical point and directly measure the disappearance of its order parameter, thereby isolating the key physical mechanisms. Cr, the elemental antiferromagnet, offers an extraordinary opportunity to investigate the fundamental question of how magnetism emerges in metals as its spin and charge order is suppressed by pressure. Tuning the Mott-Hubbard metal-insulator transition with pressure in NiS2 similarly permits experimental access to the naked quantum singularity. Finally, direct measurements of the order parameters in CeFe2, a material sitting on the knife edge between ferro- and antiferromagnetism, should permit hard conclusions to be drawn about the possible coexistence of different magnetic ground states, with the potential for self-organization on the mesoscale. These model systems will inform the study of magnetism, quantum phase transitions, and correlated materials in general. The wide array of techniques, from x-ray scattering to magnetotransport, and the mix of physics, chemistry and materials science concepts, should train students well for careers in industry, the national laboratories, or academia. NON-TECHNICAL ABSTRACTMagnets form the basis of modern technology, from computer storage to power generation, but the important question of how magnetism originates is still largely unanswered. By squeezing the elemental magnet chromium to 100,000 atmospheres at nearly absolute zero temperature it is possible to reveal and study the very point where magnetic order first emerges from quantum disorder. Similarly, it is possible to explore the competition between different types of magnetic order, where the tendency of spins - the quantum property of an electron that makes it act like a little bar magnet inside a material - to line up parallel or antiparallel can be manipulated on length scales from nanometers to millimeters. Finally, this proposal will probe how magnetism can be coupled to the ability of materials to conduct or fail to conduct electricity. The wide array of techniques, from x-rays to electrical conduction, and the necessity to combine concepts from physics, chemistry and materials science, should train students well for careers in industry, the national laboratories, or academia. Bringing research perspectives to education is another emphasis, both for the P.I. and the graduate students in the laboratory. This includes public lectures, course development for both science and non-science majors, mentoring for K-8 students in the local schools, and outreach activities as part of a citywide program.

技术摘要一直是专门用于复杂且经常无序材料的量子相变的巨大活性：稀土酸化物，重型费米昂材料，过渡金属氧化物和硫化物理想情况下，人们希望将简单的，石学计量的材料调整为其量子临界点，直接直接测量其顺序参数的消失，从而隔离关键物理机制。 CR是元素抗铁磁铁，提供了一个非同寻常的机会，可以研究金属中磁性如何在金属中出现的基本问题，因为其旋转和电荷顺序被压力抑制。在NIS2中使用压力调整Mott-Hubbard金属绝缘子的转变，同样允许实验访问裸量子奇异性。最后，应直接测量CEFE2中的顺序参数，这是一种位于铁磁和抗铁磁磁性之间的刀边缘上的材料，应允许对不同磁接地状态的可能共存得出艰难的结论，并有可能在上面进行自我组织的潜力中尺度。这些模型系统将为磁性，量子相变和相关材料的研究提供信息。从X射线散射到Magnetotransport以及物理，化学和材料科学概念的混合，各种各样的技术应该很好地培训学生的行业，国家实验室或学术界的职业。从计算机存储到发电的非技术抽象磁体构成了现代技术的基础，但是磁性如何发起的重要问题仍然在很大程度上没有得到答复。通过将元素磁铁铬挤压到几乎绝对零温度下的100,000个气氛，可以揭示并研究磁性序列首次从量子障碍中出现的点。同样，可以探索不同类型的磁性阶段之间的竞争，其中旋转的趋势 - 电子的量子特性，使其在材料内部的作用像是小磁铁 - 可以平行或对抗平行。从纳米到毫米的长度尺度。 最后，该提案将探讨如何将磁性与材料传导或无法传导电力的能力耦合。从X射线到电气传导，各种各样的技术以及结合物理，化学和材料科学概念的必要性，应该很好地培训学生的行业，国家实验室或学术界的职业。将研究观点带入教育是另一种重点，既是P.I.和实验室的研究生。这包括公开讲座，科学和非科学专业的课程发展，为当地学校的K-8学生提供指导以及作为全市计划的一部分外展活动。