Latest News         Latest work on Ni-doped Superconductors posted: Effective carrier type and field-dependence of the reduced-Tc system SrFe2-xNixAs2 (submitted): This work discusses measurements of the Hall effect, thermoelectric power, magnetic susceptibility and upper and lower critical fields of single crystals of SrFe2-xNixAs2. In this system, Ni substitution results in a dominant electron-like response, consistent with electron doping in other similar systems, and a superconducting state with large upper critical fields that greatly exceed conventional estimates of paramagnetic and orbital limits.   MURI Grant Awarded!! As part of a five-team proposal headed by Prof. Richard Greene, our group has been awarded one of four Defense Dept. awards from the highly competitive federal Multidisciplinary University Research Initiative (MURI) program.  The program supports a large-scale effort to search for new superconducting materials, and includes teams led by Paul Canfield at Ames laboratory, Iowa State University, M. Brian Maple at University of California, San Diego, and Profs. Green and Ichiro Takeuchi here at Maryland. This year, Maryland Physics alone received more MURIs than the total awarded to any other university. CNAM Director Michael Fuhrer is also an awardee.         TWO PAPERS now published on growth, characterization and properties of iron-arsenide based superconductors: 1. Superconducting and Ferromagnetic Phases in Study of the new iron-based superconducting material SrFe2As2 (Physical Review Letters): This paper discusses the peculiar observation of a 21 K superconducting phase in as-grown samples of this nominally non-superconducting parent compound and its relation to the presence of crystal lattice strain and magnetic order. 2. Evolution of Bulk Superconductivity in SrFe2As2 with Ni Substitution (Physical Review B): This paper introduces the first study of Ni substitution in this compound, which both suppresses an antiferromagnetic/structural phase transition and induces a superconducting phase with increasing Ni content, much like several other transition metal substitution series in these materials.         Crystal Growth Progress Large single crystals of superconducting Co- and Ni-doped SrFe2As2 have been successfully grown using the Central Facilities of the Center for Nanophysics and Advanced Materials. Efforts are also under way to prepare targets for thin film growth of these new materials via pulsed laser deposition techniques in collaboration with Profs. Ichiro Takeuchi of UMD Materials Science and Rick Greene of CNAM.         Research Spotlight on Wiedemann-Franz law In 1853, well before the discovery of the electron by J. J. Thomson in 1897, two German physicists named Gustav Wiedemann and Rudolf Franz made the peculiar observation that the ratio of electrical to thermal conductivities is the same in several different metals. Although not as famous as the discovery of superconductivity in mercury by Kamerlingh Onnes over fifty years afterward in 1911, this experiment marked one of the first quantitative studies of the inner nature of metals and would turn out to play a pivotal role in guiding the development of the quantum theory of solids. read more in The Photon...         2008 ICAM Workshop at Maryland The Fall 2008 Workshop on Iron-Pnictide superconductors has been announced and is open for registration. This ICAM-sponsored event will be held at the University of Maryland, College Park and will bring together the leading experts in this quickly evolving field of research.         Dilution Fridge in Operation!! Our dilution refrigerator has reached an official base temperature of 10 mK ! Work is under way to implement an experimental platform to utilize this new capability in CNAM for low temperature studies.         Fermi Surface Reconstruction   Report on Quantum Oscillations experiments through the composition-tuned Quantum Critical Point in the Ce-based '115' heavy-fermion system now published in  Physical Review Letters.         Superconductivity in ALL THREE 115 materials Deep below the onset of incommensurate magnetic order in CeRhIn5, a significant fraction of the remaining density of electronic states undergoes a bulk superconducting transition at 110 mK. We show that the thermodynamic nature of this transition is quite similar to that found throughout the 115 series, confirming the ubiquitous presence of pairing instabilities in this family of materials even far from criticality. [Phys. Rev. B. Rapid Communications]                Two Major Papers Published Study of Kondo Lattice Coherence in CeCoIn5 published in Nature Physics. Report of Violation of the Wiedemann-Franz Law at a Quantum Critical Point published in Science (1 June, 2007).