Speaker Institution : The University of Texas at Austin
Title: Study of Complex Ordered Dynamics in Spatially Random Systems by SQUID Magnetometer
Abstract : A random magnetic alloy with competing magnetic interactions (“frustration”) exhibits strongly correlated behavior in phase space. This coherence is termed as “spin glass,” and the insights gleaned from its dynamics are applicable across a broad sweep of condensed matter. By a careful choice of spatial dimension and time scale, one can prepare correlated regions that exhibit complex dynamical properties based on an “ultrametric” symmetry. Ultrametricity can be represented as a hierarchical tree-like structure, with measureable branching characteristics.
Because spin glasses are non-linear dynamical systems, their properties depend strongly on the preparation of the initial state. We have probed the dynamical properties of spin glasses prepared to provide explicit observation of the dynamical correlation length. Once measured, we have used spatial and time domains to isolate ordered spin glass states. We have measured the hierarchical nature of the ultrametric tree through the analysis of the dynamical susceptibility. Our proposed experiments will explicitly measure the probability of branching, and the branching ratio. That a completely random magnetic alloy can obey a structured phase space geometry is a remarkable property of nature, and an example of “order in randomness”.