David R. Nelson
David Nelson's research focuses on collective effects in the physics and chemistry of condensed matter. He has been interested, in particular, in the interplay between fluctuations, geometry and statistical mechanics. In collaboration with his Harvard colleague, Bertrand I. Halperin, he is responsible for a theory of dislocation-mediated melting in two dimensions. The prediction of Halperin and Nelson of a fourth "hexatic" phase of matter, interposed between the usual solid and liquid phases, has now been confirmed in experiments on thin films and bulk liquid crystals. Nelson's research includes a theory of the structure and statistical mechanics of metallic glasses and investigations of "tethered surfaces", which are two-dimensional generalizations of linear polymer chains. These fishnet-like structures exhibit a remarkable low temperature flat phase upon cooling. Nelson has also studied the flux line entanglement in the new, high temperature superconductors. At high magnetic fields, thermal fluctuations cause regular arrays of flux lines to melt into a tangled spaghetti state. The physics of this melted flux liquid has important implications for many of the proposed applications of these new materials. His current interests include vortex physics, the statistical mechanics of polymers, topological defects on frozen topographies and biophysics.
Administrative Assistant: Liz Alcock
17 Oxford Street
Cambridge, MA 02138