Raymond Osborn

Raymond Osborn is a Senior Scientist in the Materials Science Division of Argonne National Laboratory, which he joined in 1992 following post-doctoral research at the University of Oxford and a staff position at the ISIS Pulsed Neutron Source. His research is in the field of strongly correlated electron systems probing spin, charge and orbital correlations using neutrons and x-rays. His scientific interests have included quantum critical scaling in f-electron systems, the role of polaron correlations in colossal magnetoresistance, phase competition in iron arsenides, and structural fluctuations in systems with strong spin-orbit coupling. The importance of understanding disorder in such phenomena led to the development of more efficient methods of measuring single crystal neutron and x-ray diffuse scattering. He is a Fellow of the American Physical Society and the Neutron Scattering Society of America and was awarded the University of Chicago Distinguished Performance Award in 2006.

Abstract Title: A Sweeping View of Correlated Electrons in Four Dimensions

Abstract:

Neutron scattering has played a significant role in our understanding of correlated electron systems, from the measurement of coherent magnetic excitations in itinerant magnets to local spin fluctuations in heavy fermions. The advent of pulsed neutron instrumentation in the 1980s with large fluxes of epithermal neutrons extended the dynamic range to enable the first measurements of rare-earth intermultiplet transitions, quantum critical scaling in non-Fermi liquids, and the neutron resonance in iron arsenide superconductors. Time-of-flight spectrometers were also used to measure coherent spin waves but it was the development of 4D-S(Q,ω) methods by Perring and Ewings that have, in my view, provided the most significant advances in inelastic neutron scattering since Brockhouse. In 1984, Sinha had discussed the feasibility of using neutrons to probe one-electron bands through the Lindhard susceptibility. He concluded that the cross sections would be too weak in most metals but might be strongly enhanced in intermediate valence compounds. His prediction was vindicated over thirty years later with 4D-S(Q,ω) measurements on CePd3, which are in excellent agreement with DMFT calculations. I will also discuss how limitations in measuring polaronic disorder in CMR manganites led to the proposal to build CORELLI at the SNS, as well as the development of complementary x-ray methods, which have demonstrated the importance of understanding inhomogeneity in correlated electron systems.