Research

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. Our research is rooted in the growth of single crystals, which at present includes image furnace, flux and electrolytic deposition techniques. We perform neutron and X-ray scattering, transport and nonlinear response experiments. The crystals grown in our laboratory are furthermore investigated by experts in the use of complementary experimental techniques; at present, we have established well over a dozen such collaborations. As the most powerful magnetic and structural probes of condensed matter, neutron and X-ray scattering experiments play invaluable roles in our endeavors, 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. We also pursue new research directions that involve electrostatic, electrochemical and plastic deformation control of materials, as well as novel nonlinear magnetic response measurements.

A major research focus of ours is on complex oxides such as the cuprates and perovskite titanates and, more recently, also on non-oxide superconductors and charge-density-wave systems. Topics include: the evolution from Mott insulator to metal; the pseudogap phenomenon in the cuprates, and the differences between electron and hole doping in these high transition-temperature (T_c) superconductors; why T_c is very high in some materials, but not in others; the nature of coexisting and competing phases; the role of structural and electronic inhomogeneity; accessing new phases of matter via electrostatic, electrochemical and plastic deformation control.

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. Our work on ionic electrostatic and electrochemical control of materials is supported through the University of Minnesota NSF MRSEC grant.