TITLE: Surfaces: a playground for physics with broken symmetry in reduced dimensionality

SPEAKER:

TIME: Thursday Nov. 11, 1999 at 4 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

Undoubtedly, the future of condensed matter physics (CMP) lies with complexity, both in materials and in phenomena. Complexity can be viewed as the fountain of youth for condensed matter physics. If you push the frontiers of complexity new emergent phenomena will be discovered. Many of the most intriguing systems involve electron correlation effects, such as superconductivity, heavy Fermions, and colossal magenetoresistance. The concepts of reduced dimensionality and broken symmetry are key to understanding the basic physics. We the surface community are ideally situated to make major contributions to the field of CMP. Surface properties are by their very nature a result of broken symmetry and artificial structures can be fabricated that are two, one or zero dimensional. In general, in complex highly correlated materials, local properties are important leading to inhomogeneities in electronic arrangement, mico-phase separation, or striped phases. Surface scientists have the ideal tool to study this behavior, the scanning tunneling microscope. Several examples will be utilized to illustrate the possibilities for the future. (1) The effect of defects in a two-dimensional phase transition. (2) Surface stabilized magnetism in the p-wave superconductor Sr₂RuO₄, and (3) A visualization of electronic inhomogeneities at the surface of the perovskite La_0.5S_1.5MnO₄.