New Opportunities from Fabricated Materials

P. Chris Hammel
Los Alamos National Laboratory
MST-10, MS K764
Los Alamos, NM  87545
(505) 665-0759
(505) 665-7652 FAX
pch@lanl.gov

Correlated electronic systems such as cuprate superconductors derive many of their interesting and technologically important properties from non-linearities arising from competing interactions. This kind of competition leads to segregation of charge into stripes. This is clearly observed in the lanthanum cuprate materials, and these phenomena are probably important for the majority of cuprates. The delicate interplay between the charge stripes and the underlying magnetism of the cuprates determines the ground state achieved at low temperature; the possible ground states might be antiferromagnetic, glassy or superconducting.

The ability to artificially structure materials has accelerated dramatically with the development of new techniques such as molecular beam epitaxy, scanning probe microscopy, nanofabrication, and self-assembly to name a few. This ability has led to materials with new properties and capabilities For example layered systems composed of alternating ferromagnetic and metallic materials are used as sensitive magnetic field sensors that enable a new generation of high density magnetic storage. A proposal has been made by Bruce Kane to use artificially structured arrays of phosphorus atoms embedded in silicon as the fundamental elements in a solid state quantum computer. Both of these technologically important examples of artificially structured materials rely crucially on highly non-linear magnetic interactions between the elements incorporated into the materials. Understanding of these systems is far from complete.

Studies of artificially structured materials of a broad variety (for instance artificial stripes or ladders) can be envisioned as means to better understanding complex correlated electronic systems such as the cuprates. At the same time the understanding developed in years of working with magnetic materials will certainly be important in developing and optimizing devices based on artificially structured materials. Artificially structured materials provide an opportunity, then, to study new regimes of magnetic interactions relevant both to understanding correlated electron behavior and to developing important technologies.