Rare-earth transition-metal pnictides: Heavy -fermion behavior versus magnetism and superconductivity

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In Ce-based iron-pnictides, mixed-valent or heavy-fermion behavior of the Ce 4f states is in direct competition to other electron-correlation effects like magnetic order, superconductivity, and spin-density wave (SDW) formation that lead to interesting material properties which depend critically on parameters like chemical composition or external pressure. The interplay of these correlation phenomena will be studied by means of angle and spin-resolved photoelectron (PE) spectroscopy with synchrotron radiation on the basis of structurally well-characterized single-crystalline samples. Momentum (k-vector) dependent interactions between Ce 4f and particularly Fe 3d -derived bands are expected to lead to dispersions and energy-splittings of the resulting quasi-particle bands that determine the Fermi surfaces and may be visualized by means of PE. Experimental data from single-crystalline samples will be taken as a function of temperature and chemical composition and will be discussed within an approach to the periodic Anderson-model (PAM) that is solved by dynamical meanfield theory (DMFT) using non-crossing approximation (NCA) as impurity solver and results of band-structure calculations for the non-hybridized valence-band (VB) states.