Correlated-electron materials provide myriad opportunities to discover and study novel fundamental magnetic, structural, and electronic phenomena and phases, and it seems likely that only a small fraction of their scientific and technological potential has been realized so far. As the most powerful magnetic and structural probes of condensed matter, neutron and X-ray scattering experiments play invaluable roles in this endeavor, as they provide essential information about new phases of matter and the transitions between them. The importance of these experimental techniques has been recognized throughout the world, and motivated the upgrades of facilities and the construction of new ones, such as Spallation Neutron Source (SNS) and the National Synchrotron Light Source II. The crystal-size requirements for inelastic neutron scattering experiments are particularly demanding, and often can be met only through a very focused growth effort.
Our research involves state-of-the-art crystal growth and cutting-edge scattering and transport measurements. We are investigating some of the timeliest and intellectually most challenging topics in the field of correlated-electron materials, including: The role of disorder in model low-dimensional quantum magnets; the fundamental differences between electron and hole doping of the high transition-temperature (Tc) superconductors; why Tc is very high in some materials, but not in others; the role of coexisting and competing phases; the nature of magnetic and charge excitations in these and related non-superconducting materials; the nature of the metallic state in doped Mott insulators.
The quantum materials that we study are all transition metal oxides, as this vast materials class embodies many of the most fundamental and exciting contemporary questions pertaining to the quantum behavior of interacting electrons. We pursue a comprehensive approach through extensive collaborations with experts in the use of complementary experimental techniques, such as photoemission, scanning tunneling microscopy, and optical spectroscopy. At present, we have established well over a dozen such collaborations.
Most of our work is supported by the Department of Energy, Office of Basic Energy Sciences through the University of Minnesota Center for Quantum Materials. In addition, through a NSF MRSEC grant, we have begun to use synchrotron X-rays to study electrostatically doped films of complex oxides, such as cuprates, cobaltites and titanates.