Non-Fermi liquid behavior with and without quantum criticality in Ce 1−x Yb x CoIn 5 Carmen C. Almasan, Kent State University, DMR One of the greatest challenges to Landau’s Fermi liquid theory – the standard theory of metals - is presented by complex materials with strong electronic correlations. In these materials, non- Fermi liquid transport and thermodynamic properties are often explained by the presence of a quantum phase transition which happens at a quantum critical point (QCP). A QCP can be revealed by applying pressure, magnetic field, or changing the chemical composition. In the heavy- fermion compound CeCoIn 5, the QCP is assumed to play a decisive role in defining the microscopic structure of both normal and superconducting states. However, the question of whether QCP must be present in the material’s phase diagram to induce non-Fermi liquid behavior and trigger superconductivity remains open. Here we show (see right figure) that the full suppression of the field-induced QCP (H QCP ) in CeCoIn 5 by doping with Yb has surprisingly little impact on both unconventional superconductivity (T c continues to decrease linearly with doping x) and non-Fermi liquid behavior. This implies that the non-Fermi liquid behavior could be a new state of Evolution of the field induced quantum critical point H QCP, coherence temperature T coh, superconducting critical temperature T c of Ce 1−x R x CoIn 5 (R = Yb, La) as a function of rear-earth concentration x. matter in its own right rather then a consequence of the underlying quantum phase transition. Also, our results show that superconductivity and quantum criticality are likely to be decoupled in this system, i.e., unconventional superconductivity is not triggered by spin fluctuations.

Non-Fermi liquid behavior with and without quantum criticality in Ce 1−x Yb x CoIn 5 Carmen C. Almasan, Kent State University, DMR Education An essential activity performed has been the education of three graduate students and one postdoc. They did not only pursue cutting edge science, but they also became knowledgeable in a highly varied array of skills, technologies, and forefront topics in condensed matter physics by being involved in all phases of their project. These phases may include equipment and electronics design and construction, experiment “debugging”, data acquisition and analysis, and comprehension of and comparison with the relevant theoretical results. The postdoc Tao Hu is presently an Associate Professor of Physics at the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China, while the continuing Ph. D. students are Derek Haney, Xinyi Huang, and Yogesh Singh. Outreach As part of the outreach activities of the PI, underrepresented Honors Physics students from nearby high schools visited her laboratory and learned about physics in general and superconductivity and magnetism in particular, through demonstrations and short lectures given by the PI and her graduate students. These inspirational activities exposed them to a research envi- ronment and gave them a flavor of the science done in the lab and the technology involved in doing it. In addition, the PI continued to be involved in the Young Women’s Summer Institute, which is a competitive program across Ohio for middle school girls, held on the Kent State University Campus. During this program, middle school girls are exposed to science experiments and interact with female scientists at different stages in their career. Graduate student Derek Haney describes to high school students the demos he is about to show them.