ICAM Perspective and Brief Presentation
Alan Bishop
Los Alamos National Laboratory
T-11, MS B262
Los Alamos, NM 87545
(505) 667-6491
(505) 665-4063
The demands of modern materials for technology and the humbling experience of high-temperature superconductors, coupled with remarkable advances in synthesis, measurement, simulation and modeling over the last decade, are driving conceptual shifts in approaches to electronic and structural materials.
I believe that the central feature of this new era in materials science is that multiscale complexity is both intrinsic and functional in many (perhaps most) modern (and many ìoldî!) materials. This realization means that we must learn to use complexity rather than avoiding it or attempting to ìengineerî it away ó the complexity is in fact fundamental to the science of ìsynthesis-structure-propertyî relationships that must be controlled for predictive design of new generations of materials. This represents the reality of new materials driving new science techniques and concepts; in turn, this new science will drive new materials and enable new technologies ó if we develop the necessary new scientific principles and techniques.
The intrinsic complexity is characteristic of wide classes of both electronic and structural, classical and quantum, organic and inorganic materials, and crosses traditional boundaries between chemistry, solid state, materials science and biophysics disciplines. The principal common ingredient is the existence of strong ìmicroscopicî competitions leading to correlated space-time patterns at various ìmesoscopicî scales, which in turn control functionalities at ìmacroscopicî spatial scales and long times. Controlling these ìmicro-meso-macroî relationships requires understanding them. This necessitates their measurement: there is an urgent need for coordinated suites of experimental probes to measure relevant spatial and (related) temporal scales. Similarly, there is need for theory, modeling and simulation tools which can (a) extract relevant information from the new experimental probes, (b) use the information to validate minimal models, and (c) place the information in multiscale modeling frameworks with the aim of establishing a predictive hierarchical capability. This strategy inevitably means that we accept the need to augment on traditional tenets of solid state methods, field-theoretic scaling, etc., of recent decades ó beyond measurement or modeling restricted to average or asymptotic properties, ìsingle crystalsî, high-symmetry modes, band structure, Fermi liquids, critical exponents, etc.
My present interests are:
Codifying sources of multiscale complexity in space and time. In particular from coupling of spin/charge/lattice/orbital degrees-of-freedom, long- and short-range interactions, effects of disorder and dimensionality.
Modeling consequences of competitions: Nonlinearity; Frustration; Nonequilibrium; Nonergodicity; Glassiness and metastability; Global sensitivity to small and/or local internal or external perturbations.
Applications:
Thermal- and field-driven collective and multi-time scale dynamics in friction surface growth flux flow in superconductors. Especially ìglassyî evolution, relaxation and aging through the dynamics of mesoscale ìdefectsî.
Charge-and-energy localization and transduction in classical and quantum discrete systems (excitons, polarons and multiquanta bound states). Especially lattice-assisted transfer mechanisms.
Structure-function relations in complex organic and inorganic materials, emphasizing the coupling of spin, charge and lattice degrees-of-freedom -- from multiscale, directional polarizability (including charge transfer, localization and ordering) to multiscale, directional elasticity (including twinning, tweed and other fine-scale structures), and their probable interdependence. Much research in (organic and inorganic) ìcorrelated electronî materials has emphasized spin and charge but must include lattice, and competitions between ìintrinsicî and ìextrinsicî disorder, to realistically encompass multiscales. I am particularly concerned with solid-solid phase transformation and metal-insulator transitions and quantum critical points and the many attendant length and timescales and sensitivities of competing phases) -- in transition metal oxides and heavy-fermion compounds, organic C-T salts, conjugated electronic polymers, and pinned charge-density-wave materials. In all these cases, the crossovers between global broken-symmetries are much richer than homogeneous-homogeneous phase transitions ñ there is evidence for intrinsic long-period coexisting, glassy phases, etc.
Organic-inorganic hybrid materials, including interfaces and membranes, emphasizing engineered multifunctional complexes. Especially heterostructures, surfactants, nonplanar surfaces and thin-film growth and morphology for structural, electrooptics, sensing, transduction, etc. This is both learning from natural materials (biomimetic materials based on natureís strategies of assembly and functionalization (charge-transfer, electrostatic interactions, etc.)), and may also guide the use of techniques from other disciplines to probe biomolecular function (gene expression, etc.).
PROPOSED PRESENTATION
ìCompeting Short-and Long-Range Interactions in Hard and Soft Matterî
We use examples from our current research to demonstrate how the same concept of ìcompeting interactionsî leads to intrinsic inhomogeneities and global sensitivities. The examples are: Filamentary flux flow in superconducting films; Charge-ordering in transition metal oxides; Fine-scale textures at solid-solid structural phase transformations; and Charge-ordering in polyelectrolytes.
Collaborators: A. Castro-Neto, N. G. Jensen, T. Lookman, A. Saxena, B. Stojkovic