Education

1. Superconducting and magnetic anisotropy ofLnFePO(Ln = La, Pr, Nd) single crystalsM. Brian Maple, University of California-San Diego, DMR 0802478 The iron-pnictide/chalcogenide (Fe-Pn/Ch) compounds have attracted intense interest recently, largely due to the observation of high-temperature superconductivity (SC) throughout a broad range of crystal structures, all of which include corrugated Fe-Pn/Ch layers. The highest SC transition temperatures (Tc) are observed for the optimally doped LnFeAsOcompounds (Ln = lanthanide). Less attention has been paid to the P-based samples, which have lower Tc’s, although variations of these compounds show enhanced SC.One of the most intriguing issues is whether the SC of Fe-Pn/Chmaterials has the same origin. Support for a common mechanism of SC is provided by the observation that the Pn/Ch-Fe-Pn/Chbond angle is correlated with Tc. On the other hand, the introduction of magnetic Ln ions enhances Tc for the Fe-As compounds, but reduces Tc in the Fe-P analogs. We undertook a study of single crystals of LnFePO (Ln = Pr and Nd) in order to address the effectof Ln magnetic moments on the SC in this system. Measurements of the upper-critical-field curves and the magnetic susceptibility reveal that the magnetic-field-induced suppression of the superconducting state is not strongly correlated with spin polarization of the magnetic lanthanide ions. Upper critical field Hc2vsT for H parallel and perpendicular to the abplane for PrFePO (left panel) and NdFePO (right panel). R. E. Baumbach, J. J. Hamlin, P.-C. Ho, I. K. Lum, and M. B. Maple, Phys. Rev. B 85, 104526 (2012)

2. Superconducting and magnetic anisotropy of LnFePO(Ln = La, Pr,Nd) single crystalsM. Brian Maple, University of California-San Diego, DMR 0802478 Education Individuals at different stages of their careers (three Assistant Professors, one Associate Professor, four postdocs, three graduate students, four undergraduates – including one who participated in the research experience for undergraduate [REU] program, and a Quantum Design, Inc. research scientist) have been involved in this ongoing research. Lei Shu and Marc Janoschekcontinue to work on the project (currently studying the electronic structure of Ce1-xYbxCoIn5 from spectroscopy and bulk properties), several of the undergraduate students are still with us in the lab. J. J. Hamlin, currently an Assistant Professor at the University of Florida, is pursuing related research projects. Outreach Our lab has a strong commitment to increasing awareness and understanding of the importance of experimental physics to a variety of communities. We currently teach an advanced physics lab (Physics 133) at the University of California, San Diego, where students are required to plan and carry out a research project, and then present the results to their peers in the class. Additionally, each year we perform regularly scheduled demonstrations at nearby elementary schools in which we display some of the interesting aspects of low temperature physics including superconductivity and the behavior of various materials when they are cooled to 77 K with liquid nitrogen. Top: A member of our lab demonstrates the properties of liquid nitrogen to undergraduate students. Bottom: Using liquid nitrogen, we discuss and demonstrate the characteristics of a high temperature cuprate superconductor.