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Department of Physics

Dr. Michael Graf

associate chairperson and professor of physics

michael-graf

Phone: 617-552-4128
Higgins Hall 230B
E-mail: michael.graf@bc.edu


Education

Ph.D., Physics, Brown University
B.S., Physics/Math minor, Rensselaer Polytechnic Institute

Awards

  • IBM Postdoctoral Fellowship, 1987
  • Boston College Distinguished Junior Faculty Award, 1991
  • Research Opportunity Award, Research Corporation, 1997

Areas of Research

My work focuses on the properties of condensed matter systems at low temperatures and in strong magnetic fields. Early in my career this included studies of the growth kinetics of helium crystals, electrical transport and optical properties of two-dimensional electron systems (GaAs-AlGaAs quantum wells, GaSb-InAs semi-metallic quantum wells), and optical properties of the semi-magnetic semiconductor Cd0.95Mn0.05Se:In near the metal-insulator transition. The recent emphasis of my research has been on novel electronic systems, which provide opportunities to further our understanding of fundamental physical principles as well as to develop unique electronic devices.

Research conducted by me and my collaborators at the University of Amsterdam (Dr. A. de Visser) on the heavy-fermion superconductor UPt3 (sponsored by grants from Petroleum Research Fund and Research Corporation) has an ultimate goal of understanding unconventional superconductivity, magnetism, and their interplay in these strongly-correlated systems. The U(Pt1-x,Pdx)3 system is particularly interesting, as Pd-substitution affects both the striking double superconducting transition — it is the only known way to increase the splitting — and the anomalous antiferromagnetic state observed in the pure compound. We pursue these goals through specific heat, resistance, muon spin rotation measurements (in collaboration with colleagues from the Paul Scherrer Institute and ETH-Zurich), cantilever magnetometry, and neutron scattering measurements for samples in zero and applied magnetic fields, and also under hydrostatic pressure (in collaboration with colleagues from the National High Magnetic Field Laboratory), with particular emphasis on delineating the temperature-Pd-concentration phase diagram, which dramatically demonstrates the competition between superconductivity and static antiferromagnetic order.

Another class of interesting materials is the composite formed by injecting metals into an ordered porous insulating host material, such as indium or bismuth into Vycor glass, or into sub-micron nanochannel arrays (in collaboration with colleagues from Howard University). In our most recent work we have tracked the effects of confinement on the Fermi surface through magnetoquantum oscillations (Shubnikov-de Haas and de Haas – van Alphen effects). The Bi-based compounds may have important technological applications in the area of solid-state thermoelectric cooling.

New projects, developed with colleagues at the NMR/NQR Group at the University of Pavia, include studies of strong magnetic fields on the quantum critical material CeCu5.9Au0.1, and probing quantum tunneling of magnetization in LiY0.998Ho0.002F4 through NMR and µSR spectroscopies.

Much of the work described above is carried out in my laboratory at Boston College, where I have a He-3 adsorption refrigerator and a He-4 recirculation refrigerator, used in conjunction with 10 T and 3 T superconducting magnets, respectively.

Recent Presentations

"Probing the Interplay Between Magnetism and Superconductivity in UPt3 via Pd Substitution," presented at the Boston College Workshop on Magnetically Mediated Superconductivity and as an invited lecture at the 2001 APS March Meeting.

Selected Publications