Emerging Functionality in Transition-Metal Compounds Driven by Broken Symmetry, Reduced Dimensionality, or Spatial Confinement

It is becoming increasingly clear that the exotic properties displayed by correlated electronic materials （CEMs） such as high-Tc superconductivity in cuprates, ＂colossal＂ magnetoresistance （CMR） in manganites, and heavy-fermion compounds are intimately related to the coexistence of competing nearly degenerate states which couple simultaneously active degrees of freedomcharge, lattice, orbital, and spin states ^1]2]. The striking phenomenon associated with these materials is due in large part to spatial electronic inhomogeneities, or nanoscale phase separation, in many of these hard materials, the functionality is a result of the soft electronic component that leads to self-organization. Birgeneau and Kastner wrote in the introduction to the issue of Science dedicated to CEMs, ＂A remarkable variety of new materials have been discovered that cannot be understood at all with traditional ideas＂ ^1].One of the grand challenges of materials science is, How do complex phenomena emerge from simple ingredients ^3]. A challenge which in many ways is more important, is understanding the evolution of this complexity in an environment of Broken Symmetry, Spatial Confinement, or Reduced Dimensionality. This lecture will illustrate that Broken symmetry, reduced dimensionality, and spatial confinement are promising routes for the discovery of emergent physical phenomena in complex transitionmetal compounds.