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

非技术摘要超导体导电没有任何阻力，提供了引人入胜的新科学和重要的新技术(从医学成像到高能粒子加速器，从电信过滤器到磁悬浮列车)。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。该奖项支持对新材料的研究，这些材料在显著更高的温度下超导，并挑战了我们对超导的理解。在过去的三十年里，这些高温超导体因其丰富且往往悬而未决的行为以及它们的技术应用而引起了人们的极大关注。纽约州立大学布法罗分校的研究人员使用他们开发的新红外线技术来探索这些材料如何随着化学成分、磁场、温度和探测频率的变化而表现出来。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影响。技术摘要该奖项来自材料研究部凝聚态物理项目，支持纽约州立大学布法罗分校的铜酸盐和铁镁高温超导体(HTS)研究。在过去的三十年里，高温超导材料因其丰富且往往悬而未决的行为以及它们的技术应用而引起了人们的极大关注。由于其中许多性质的特征能量标度，以及磁偏振技术探测电子结构中的不对称性和有序性的独特能力，这些高温超导非常适合使用太赫兹(2-6 mev)和红外(IR：100-1200 mev)霍尔测量进行探测。首席研究员研究了各种高温超导材料随掺杂、温度、探头能量和磁场的变化。所提议的测量的灵敏度和广谱范围提供了对这些高温超导材料中不寻常的赝隙相(PGP)的新见解，以及关于电荷、自旋和磁有序的新信息。铜酸盐中的一个关键问题是，PGP是否只是超导电性的前驱，或者它是否是一个完全成熟的新相，它的对称性被打破了。其目的是提供对(S)打破对称的机制的洞察。在铁粒子中，这项工作探索了广泛的反常行为，包括远远高于超导禁带的反常光吸收，红外光谱中异常的光谱重量转移，磁性和超导可能共存，自旋有序，以及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.