The interplay between theory and experiment is particularly lively. Members of the condensed-matter group also frequently collaborate with researchers in other disciplines -- such as Chemistry, Geophysics, Atmospheric Sciences, Electrical Engineering, and Materials Science and Engineering -- and with groups at several other universities and laboratories in the US and other nations.
Experimental condensed matter research at the UW can be loosely divided into three overlapping areas: fabrication and properties of nanostructures and surfaces, structural aspects of materials, and ice physics.
The Low Temperature Laboratory (Vilches) probes the properties and phase diagrams of two-dimensional films of quantum solids, for example various isotopes of hydrogen and helium on graphite or MgO substrates. The principal techniques are calorimetry and other thermodynamic techniques, optical reflectometry, and, in collaboration with European laboratories, neutron diffraction and quasi elastic neutron scattering.
The research program of the Surface Properties Laboratory (Fain) is currently concentrating on the use of scanning probe microscopy to investigate surface forces and interactions. Of particular interest are the nanoscale mechanical properties of the ice surface and its interface with solid materials. Other projects utilize high resolution low energy electron diffraction and Auger electron spectroscopy for the study of structures and phase transitions in adsorbed monolayers and thin films.
Research in the Heteroepitaxial Growth Laboratory (Olmstead) focuses on understanding both the mechanisms of thin film growth and the unique properties of the resultant low-dimensional structures. Experiments probe the development of electronic, optical and atomic structure during growth of crystalline films on dissimilar substrates, using combined facilities for molecular beam epitaxy and materials characterization. Of particular interest are nanostructures combining silicon with another material of very different atomic and electronic structure, for example an ionic insulator or a van der Waals semiconductor.
The X-Ray Scattering Laboratory (Sorensen) focuses on structural and dynamical studies of surfaces under electrochemical conditions, crystalline superlattices, and freely suspended liquid crystal films. Research performed at the UW uses a high intensity rotating anode x-ray generator and two high precision computer- controlled goniometers in combination with scanning probe microscopy. The research also employs very intense synchrotron x- ray sources at national laboratories to study the same systems.
Several adjunct faculty members also study nanostructures and surfaces. Research projects in chemistry, bioengineering and materials science involving physics graduate students include: growth morphologies of model catalysts, using scanning probe microscopy and various ion and electron spectroscopies (Campbell); etching of semiconductor surfaces, using molecular beam scattering and scanning probe microscopy (Engel); optical and structural properties of biologically relevant materials, using light scattering and both optical and scanning probe microscopies (Vogel); growth and properties of semiconductor nanostructures, using chemical vapor deposition, molecular beam epitaxy, and a number of optical, electronic, x-ray, and microscopic characterization tools (Pearsall).
In the XAFS Laboratory (Stern), x-ray absorption and scattering techniques are being applied to study the nucleation of melting by impurities, the structural changes in ferroelectric and antiferroelectric displacive transitions, the local structure in disordered materials, and the local structural variation in high temperature superconductors. Anomalous diffuse x-ray scattering and Raman scattering (Seidler) are used as complementary probes in measurements of ion-pairing in chemical solutions where the solvent is beyond the liquid-vapor critical point; these studies have immediate relevance for the use of supercritical chemistry in toxic waste remediation.
In the X-Ray Scattering Laboratory (Sorensen), the new technique of x-ray holography is being developed. This technique exploits x-ray fluorescence and bremsstrahlung radiation to obtain atomic scale information about atoms embedded in solids.
In the Microstructural Kinetics Laboratory (Seidler), research focuses on the equilibrium and non-equilibrium statistical mechanics of disordered solids and complex materials (gels, granular systems, colloids, etc.). Fluctuations in microstructure, including surface roughness, defect configurations and colloid distribution, may be strongly correlated with fluctuations in thermodynamic, electronic and optical properties. These are studied with a combination of electronic transport, light scattering and dynamical x-ray scattering techniques.
In the High Pressure Laboratory (Ingalls) very high pressures are used to vary the crystal, magnetic, electronic, and vibrational structure of materials. Primary techniques include XAFS, conducted off campus at national synchrotron facilities such as the Stanford Synchrotron Radiation Laboratory and Advanced Photon Source, and gamma-ray recoil spectrometry using Mossbauer spectrometers in the Physics Department. The high pressures are generated using the opposed anvil technique, such as with the diamond anvil cell, which is capable of pressures of several hundred gigapascals. Experimental systems studied are pure metals and metal halides, perovskites, mixed-valent materials, amorphous systems, high temperature superconductors and materials of geological significance.
An interdisciplinary group of faculty members and students is conducting wide ranging research on the fundamental and applied physics of snow and ice and their environmental manifestations (Dash, Fain, Baker, Seidler). Ice has enormous environmental importance, through the influence of snow and ice cover on the global climate, the scavenging of atmospheric pollutants by snow, stratospheric ice clouds and their role in ozone destruction, frost heave on roads and engineered structures, and freeze damage to agricultural products and soils. These phenomena depend in large degree on the molecular physics of ice and its phase transformations. Several current research projects are addressing the physical basis of ice phenomena. They include studies of nucleation and crystallization dynamics, surface melting, adhesion and friction on a nanometer scale, the microscopic mechanism of electrical charging of thunderstorms, freezing in saline and porous media, and the application of ground freezing for the management of hazardous wastes. Experimental techniques include optical polarimetry, interference microscopy, ellipsometry, thermometry, calorimetry, atomic force microscopy, dynamic light scattering, and novel crystal growth and porous media cells.
The University of Washington has recently begun a campus-wide initiative in nanotechnology, which involves several members and adjunct members of the physics faculty. The Nanotechnology User Facility will provide central equipment and technical support in the growing field of nanotechnology, especially for high resolution microscopies and spectroscopies. There are also excellent electron microscopy facilities, operated in the Department of Materials Science and Engineering, to which physics faculty and students have access.
Thanks to departmental, University, and Federal support the condensed matter group is in the process of constructing and inaugurating several new experimental facilities.
For more information on graduate opportunities in the experimental condensed matter physics group, or to schedule a campus visit, contact Prof. Marjorie Olmstead, or any other member of the experimental condensed matter faculty working on reasearch of particular interest to you.
Research in the UW Experimental Condensed Matter Physics Group is funded by several sources, including: the U.S. National Science Foundation, the U.S. Department of Energy, The Leonard X. Bosack and Bette M. Kruger Charitable Foundation, the Research Corporation, and the Alfred P. Sloan Foundation.
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