Professor Birgeneau received his Ph.D. in Physics from Yale University in 1966 with Professor Werner Wolf. He was on the faculty of Yale for one year and then spent one year at Oxford University. He was at Bell Laboratories from 1968 to 1975 and then went to MIT in September 1975 as Professor of Physics. In 1988 he became head of the department and in 1991 became Dean of Science at MIT. In 2000, he became President of the University of Toronto. In 2004 he became UC Berkeley’s Chancellor and joined the Physics faculty. He concluded his service as Chancellor at the end of May 2013 and is now the Arnold and Barbara Silverman Distinguished Professor of Physics, Materials Science and Engineering, and Public Policy. Professor Birgeneau is the co-chair of the Lincoln Project with Mary Sue Coleman, the President Emeritus of the University of Michigan. The Lincoln Project is an initiative of the American Academy of Arts and Sciences which advocates for the importance of public colleges and universities and devises strategies to increase their funding.
Professor Birgeneau's research is primarily concerned with the phases and phase transition behavior of novel states of matter. These include one and two dimensional quantum magnets, highly disordered magnets, lamellar CuO2 high temperature superconductors, and Fe pnictide and chalcogenide superconductors. He uses primarily neutron and x-ray scattering techniques to probe these systems. The neutron and x-ray scattering experiments are carried out at national facilities located in Berkeley, Stanford, Maryland, Tennessee, Canada, England, Germany and Japan. His group has also implemented state-of-the-art materials growth and characterization facilities at LBL and on campus.
The physics of highly correlated electronic materials is controlled by both quantum effects and many body electron-electron interactions. This means that both the microscopic and macroscopic properties differ dramatically from those which one would deduce using traditional one-electron techniques. The most spectacular manifestation of quantum many body behavior is high temperature superconductivity which is found in a number of doped lamellar CuO2 ceramic materials. We are pursuing a variety of strategies to elucidate the fundamental physics of high temperature superconductors with an emphasis on the interplay between microscopic antiferromagnetic spin fluctuations and the superconductivity. We are also studying related low dimensional magnetic systems in which quantum and/or frustration effects produce behavior which is fundamentally different from that manifested by the equivalent classical system.
Two decades after the discovery of the CuO2 high temperature superconductors, quite unexpectedly, an entirely new class of superconductors based on sheets of FeAs or Fe(Se/Te) has been discovered. The phase diagrams of these new superconducting systems have many similarities to that of the copper oxide superconductors but there also are some essential differences. For example, the copper oxide parent materials are invariably antiferromagnetic Mott insulators whereas for the Fe-based materials the parent materials vary from being antiferromagnetic semimetals to antiferromagnetic narrow band gap semiconductors. In the Fe systems the structural and magnetic transitions are intimately connected to each other whereas in the copper oxides the structural transition is benign. This new field is at the stage where materials discovery, materials fabrication and characterization are playing the dominant role. Accordingly, our group is focused on growing large single crystals of Fe pnictide and chalcogenide superconductors across the entire phase diagrams and characterizing the materials using bulk property measurements together with neutron and synchrotron x-ray scattering techniques as well as angular resolved photoemission spectroscopy.
M. Wang, W. Tian, P.N. Valdivia, S.X. Chi, E. Bourret-Courchesne, P.C. Dai, R.J. Birgeneau. Two spatially separated phases in semiconducting Rb0.8Fe15S2, Physical Review B 90, 2014.
C.R. Rotundu, T.R. Forrest, N.E. Phillips and R.J. Birgeneau. Specific Heat of Ba0.59K0.41Fe2As2, an Fe-Pnictide Superconductor with Tc=36.9K, and a New Method for Identifying the Electron Contribution, J. Phys. Soc. Jpn 84, 114701, 2015.
M.G. Kim, M. Wang, G.S. Tucker, P.N. Valdivia, D.L. Abernathy, S. Chi, A.D. Christianson, A.A. Axcel, T. Hong, T.W. Heitmann, S. Ran, P.C. Canfield, E.D. Bourret-Courchesne, A. Kreyssig, D.H. Lee, A.I. Goldman, R.J. McQueeney, and R.J. Birgeneau. Spin Dynamics near a putative quantum critical point in Cu-substituted BaFe2As2 and its relation to high temperature superconductivity, Phys. Rev. B 92, 214404, 2015.
M. Yi, M. Wang, A.F. Kemper, S.-K. Mo, Z. Hussain, E. Bourret-Courchesne, A. Lanzara, M. Hashimoto, D.H. Lu, Z.-X. Shen, and R.J. Birgeneau. Bandwidth and Electron Correlation-Tuned Superconductivity in Rb0.8Fe2(Se1-zSz)(2), Physical Review Letters 115, 256403, 2015.
T.R. Forrest, P.N. Valdivia, C.R. Rotundu, E. Bourret-Courchesne and R.J. Birgeneau. The effects of post-growth annealing on the structural and magnetic properties of BaFe2As2, J. Phys. C 28, 115702, 2016.