Research Interests
Professor Robert J. Birgeneau's research is primarily concerned with the phases and phase transition behaviour of novel states of matter. These include one- and two- dimensional magnets, liquid crystals, physisorbed and chemisorbed surface monolayers, clean metal and semi-conductor surfaces, graphite intercalates, highly disordered magnets and most recently, lamellar CuO₂ superconductors. He uses both neutron and X-ray scattering techniques to probe these systems. Professor Birgeneau and his collaborators pioneered the use of X-ray synchrotron radiation for high resolution studies of condensed matter. For the past decade, he and collaborators have carried out a comprehensive research program aimed at elucidating the microscopic properties of the high-T_c superconducting materials.
Research Areas
Soft condensed matter: Study of Quenched Disorder Liquid Crystals in Random Aerogel Networks
High-temperature Superconductors: Spin Fluctuations in Copper-Oxide High-T_cs
Advanced scattering probes (Synchrotron produced X-ray photons and neutrons) are used to study order and excitations of correlated electrons in numerous condensed matter systems. Scattering probes allow one to measure various orders of correlation functions and order parameters and reveal the quantum numbers (energy, momentum or spin) of electrons in crystals which describe the phase (Fermi surface topology, quasiparticle self-energy etc.) or some collective excitations such as magnons, phonons, plasmons or over the entire Brillouin zones (allowing to classify the broken-symmetry phases). Precise experimental measurements of dispersion relations (E vs. k or q) of these elementary quantum and collective excitation modes provide fundamental insights about the microscopic physics of the complex systems. We use three principal techniques:

• Inelastic, Elastic, Resonant and Coherent X-ray Scattering:
• ALS in Berkeley, California
• APS in Argonne, Illinois
• Neutron Scattering:
• NIST in Gaithersburg, Maryland
• ISIS in London, England
• C5 at Chalk River, Canada

Our group currently performs experiments at national and international laboratories (Brookhaven, Lawrence-Berkeley, SSRL/SLAC, NIST,and Chalk River). We are developing techniques and programs to utilize soft x-rays (~ 20 eV - 1000 eV) to probe disordered soft-condensed matter systems at the Advanced Light Source in Berkeley. The group also has traveling solvent floating zone (TSFZ) facilities for growing large single-crystal high-temperature superconductors as well as a 14T magnet and four-circle diffractometers for materials characterization.
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