Physics of quasicrystals and related alloys

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Advances in the field of condensed-matter physics often require the discovery and development of new materials that extend or challenge the current understanding. The proposed research addresses both the synthesis of new materials and the investigation of their physical properties. This proposal focuses on one specific class of materials that are of current interest, namely quasicrystals.In addition to the basic crystalline and amorphous structural forms of solids, a new phase of matter known as quasicrystals was discovered in 1984. This phase has a new type of long-range translational order, called quasiperiodicity, and a non-crystallographic orientational order associated with classically forbidden symmetry axes. A central problem in condensed matter physics is to determine whether quasiperiodicity leads to physical properties which are significantly different from those of crystalline and amorphous materials.How do the electrons behave in a quasiperiodic environment? What is the nature of the electronic states in quasicrystals? What magnetic ground states are allowed in quasicrystals? More than two decades after the discovery of quasicrystals, these questions are still hotly debated by researchers. The proposed research addresses these outstanding questions via the synthesis of several families of quasicrystals and corresponding crystalline approximants and the investigation of their physical properties with the magnetization, neutron diffraction, electrical resisitivity and magnetoresistance, Mossbauer spectroscopy, and photoemission spectroscopy techniques. The end product of the proposed research will be a much clearer understanding of the intrinsic magnetic, electronic transport, and electronic structure properties of quasicrystals. A dozen of graduate/undergraduate students will acquire a range of practical synthesis and measurement related skills as well as in-depth understanding of various magnetic and electronic phenomena. In addition, the availability of well-characterized quasicrystals will provide the field in general with a new toy-box of samples for investigating the physical effects of quasiperiodicity in solids.