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Principal Research Interests
Stephen Kevan's research program focuses on experimental studies of the electronic, structural, and dynamical properties of natural and synthetic low-dimensional material systems. Systems of current interest include nominally clean and adsorbate-covered surfaces, ultrathin films with unusual self-assembled 1D and 2D structures, synthetic thin films and multilayers with engineered magnetic properties, and complex materials with unusual properties derived from electron correlation and highly anisotropic structures.
Highly anisotropic materials exhibit many exotic properties, including, for example, the quantum Hall effect, high temperature superconductivity, charge- and spin-density waves, and giant and colossal magnetoresistance. In some cases, the underlying physics in these systems is not well understood. More importantly, the range of anisotropic structured materials synthesized to date is very limited. Our program provides a multifaceted approach to this area, ranging from rational synthesis to detailed characterization.
In addition to facilities available in Kevan's laboratory and shared facilities in the Materials Science Institute, a significant fraction of our characterization effort is focused upon the utilization the Advanced Light Source, a third generation synchrotron radiation facility at Lawrence Berkeley National Laboratory. This facility is optimized to produce soft x-rays in a wavelength range corresponding to the important length scales in many reduced-dimensionality phenomena and with energies that allow various spectroscopic probes to be usefully applied. An enduring focus of our program has been to measure the Fermi contours of surface-localized states, and to relate these to other surface properties such as phonon anomalies, adsorbate ordering, and other elementary excitations. Moreover, the high optical brightness of a third generation source allows for efficient spatial filtering so that other more exotic techniques can be developed and applied. Specifically, we are actively pursuing the soft x-ray analog of dynamical laser light scattering, e.g., to probe fluctuations in soft condensed matter systems. A sampling of current research projects includes:
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