Resolving competing orders and symmetry-breaking in cuprate and iron pnictide high temperature superconductors using infrared Hall measurements

超导体导电没有任何阻力，并提供了迷人的新科学以及重要的新技术（从医学成像到高能粒子加速器，电信滤波器到磁悬浮列车）。传统超导体面临的最大技术挑战之一是，它们必须使用昂贵且日益稀缺的液氦冷却到非常低的温度。该奖项支持在更高温度下超导的新材料的研究，并挑战了我们对超导性的理解。在过去的三十年里，这些高温超导体因其丰富且经常未解决的行为以及它们的技术应用而引起了人们的极大关注。位于布法罗的纽约州立大学的研究人员使用他们开发的新红外技术来探索这些材料如何作为化学成分、磁场、温度和探测频率的函数。该项目涉及研究生和本科生。该推广计划涉及布法罗的一所公立高中，将对城市混合收入公立学校的学生产生很大的影响。技术摘要这一奖项来自材料研究部的凝聚态物理计划，支持纽约州立大学布法罗分校对铜酸盐和铁磷属元素化物高温超导体（HTS）的研究。在过去的三十年里，高温超导材料因其丰富且经常未解决的行为以及其技术应用而引起了人们的极大关注。由于许多这些属性的特征能量标度和独特的能力，磁极化探测电子结构中的不对称性和秩序，这些HTS非常适合使用太赫兹Hz（2-6 meV）和红外（IR：100-1200 meV）霍尔测量的探索。首席研究员研究了各种各样的高温超导材料作为掺杂，温度，探针能量和磁场的函数。建议的测量的灵敏度和广泛的光谱范围提供了新的见解不寻常的赝隙相（PGP）在这些HTS材料，以及新的信息，电荷，自旋和磁有序。铜氧化物中的一个关键问题是PGP是否只是超导性的先驱，或者它是否是一个完全成熟的新相，具有自己的对称性破缺。目的是提供对破坏对称性的机制的深入了解。在铁磷属元素中，这项工作探索了广泛的异常行为，包括远高于超导能隙的异常光学吸收，红外光谱中不寻常的光谱重量转移，磁性和超导性的可能共存，自旋有序和PGP。 这项研究涉及本科生和两名博士生。

Non-Technical AbstractSuperconductors conduct electricity without any resistance and have provided fascinating new science as well as important new technologies (from medical imaging to high energy particle accelerators to telecommunications filters to maglev trains). One of the biggest technological challenges of conventional superconductors is that they have to be cooled to very low temperatures using expensive and increasingly scarce liquid helium. This award supports research on new materials that superconduct at significantly higher temperatures and have challenged our understanding of superconductivity. These high temperature superconductors have attracted a great deal of attention in the last three decades for their rich and often unresolved behavior as well as their technological applications. The researchers at the State University of New York at Buffalo use new infrared techniques they developed to explore how these materials behave as a function of chemical composition, magnetic field, temperature, and probing frequency. The project involves graduate and undergraduate students. The outreach program involves a public high school in Buffalo and will have a large impact on urban mixed-income public school students.Technical AbstractThis award from the Condensed Matter Physics program in the Division of Materials Research supports research on cuprate and iron pnictide high temperature superconductors (HTS) at the State University of New York at Buffalo. HTS materials have attracted a great deal of attention in the last three decades for their rich and often unresolved behavior as well as their technological applications. Due to the characteristic energy scale of many of these properties and the unique ability of magneto-polarimetry to probe asymmetries and order in the electronic structure, these HTS are extremely well-suited for exploration using terahertz Hz (2-6 meV) and infrared (IR: 100-1200 meV) Hall measurements. The principal investigator studies a wide range of HTS materials as a function of doping, temperature, probe energy, and magnetic field. The sensitivity and broad spectral extent of the proposed measurements provide new insights into the unusual pseudogap phase (PGP) in these HTS materials, as well as new information about charge, spin, and magnetic ordering. A key question in the cuprates is whether the PGP is simply a precursor to superconductivity or whether it is a fully fledged new phase with its own broken symmetry. The objective is to provide insight into the mechanism(s) breaking the symmetry. In the iron pnictides, the work explores a wide range of anomalous behavior, including anomalous optical absorption far above the superconducting gap, unusual spectral weight transfer in the IR, possible coexistence of magnetism and superconductivity, spin-ordering, and a PGP. The research involves undergraduate students and two PhD students.