Maple Group

Strongly correlated electron phenomena in novel d- and f-electron materials

The general theme of our research is strongly correlated electron phenomena in novel d- and f-electron materials. These phenomena include superconductivity, magnetism, and effects arising from their interplay, metal-insulator transitions, charge- and spin-density waves, valence fluctuations, hybridization gap semiconducting behavior, heavy fermion behavior, and non-Fermi liquid behavior. The objectives of our research are to characterize the extraordinary ordered phases found in these materials, determine the conditions under which they are formed, identify underlying microscopic mechanisms, and test relevant theories. Of particular interest are unconventional types of superconductivity found in layered copper oxide and iron pnictide high temperature superconducting compounds, in rare earth and actinide based heavy fermion compounds, and in uranium-based weak ferromagnets. We also have a strong interest in non-Fermi liquid behavior, unconventional superconductivity and exotic magnetic phases, that are found in d- and f-electron materials in the vicinity of quantum critical points, values of a control parameter such as composition, pressure, or magnetic field where a second order spin- or chargeordered phase transition is suppressed 0 K. Our laboratory has facilities for preparing and characterizing polycrystalline and single-crystal bulk and thin film samples of a broad spectrum of materials, and for measuring the transport, thermal and magnetic properties of these materials over a wide range of temperature, magnetic field, and pressure. In particular, we are interested in the study of matter under extreme conditions of low temperature down to millikelvin temperatures, magnetic fields up to 11 tesla, and pressures up to several megabars. We collaborate with groups at UCSD and other institutions on specialized measurements such as thermal expansion, transport, thermal, and magnetic measurements in extremely high magnetic fields, infrared spectroscopy, neutron and x-ray scattering, muSR and NMR, and photoelectron spectroscopy.