Experimental Studies of Metal-Insulator Transitions and Superconductivity (Materials Research)

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Professor Chaikin proposes investigations in several areas. (a) Extensions of earlier work on measurements of the transition temperature for various periodic, quasi-periodic, and random artificially produced superconducting two dimensional arrays are planned. The arrays are produced using microlithography techniques and the superconducting order parameter is used to probe solutions to the wave equation in these systems. (b) Very fine scale periodic structures will be used to impose a periodic potential in a gallium-arsenide heterostructure. Hall and magnetoresistance measurements at low temperature will be used to investigate a predicted "chaotic" behavior associated with the Landau band being split into sub-bands by the periodic potential. (c) Further experiments on the transport properties of icosahedrally packed alloys are planned. (d) Ultra-thin metallic films epitaxially grown on a semiconductor substrate will be produced. Transport and thermoelectric power measurements will be made on these systems. (e) Thermoelectric power and other properties will be studied in the new high Tc superconducting materials. The thrust of the proposed work is an investigation of electrical conduction in a variety of exotic systems. This will lead to a better fundamental understanding of electrical conduction and may be of particular relevance for microelectronics development.