This GOALI experimental research project is concerned with entirely new, three-dimensional arrays of Josephson junctions, which will be fabricated for the first time making use of advanced microlithographic techniques and facilities. An entirely new domain of behavior relating to phase transitions, model systems for high temperature superconductors, and vortex motion will be made accessible in three dimensional arrays, rather than the previously studied two-dimensional arrays of Josephson Junctions. The steps in fabricating the novel device arrays will include the deposition of multilayers, e-beam writing and mask fabrication at the Cornell University Nanofabrication Facility, and electron cyclotron resonance (ECR) etching at PlasmaQuest in Richardson Texas. In measurements on the arrays, focus will be on three-dimensional critical fluctuations in the conductivity, the susceptibility, and the critical field. Other topics of interest are modeling the three-dimensional XY Hamiltonian, the nature of frustration in 3-d spin systems, and 2- to 3-dimensional crossover effects in the phase transition. The research will involve graduate student and postdoctoral researchers who will receive excellent training beneficial to their future careers in industry, government or academic research. This work is interdisciplinary in nature and is supported in part by the Office of Multidisciplinary Activities in the Mathematical and Physics Sciences Directorate at NSF. %%% This experimental research project is in the category of Grant Opportunities for Academic Liaison With Industry (GOALI), which fosters collaboration between academic and industrial researchers. This project is concerned with entirely new, three- dimensional arrays of Josephson junctions. Josephson junctions between superconducting electrodes are highly non-linear device elements whose behavior is strongly influenced by magnetic fields, even at the level of the single "flux quantum". For this reason Josephson Junctions are in fact used in sensitive magnetic field detectors. Arrays of Josephson Junctions are model systems for the motion of magnetic flux in superconductors and also for studying phase transitions. An entirely new domain of behavior relating to phase transitions, model systems for high temperature superconductors, and vortex motion will be made accessible in three dimensional arrays, rather than the previously studied two- dimensional arrays of Josephson Junctions. The steps in fabricating the novel device arrays will include the deposition of multilayers, e-beam writing and mask fabrication at the Cornell University Nanofabrication Facility, and electron cyclotron resonance (ECR) etching at PlasmaQuest in Richardson Texas. Because the systems to be studied are models for other types of physical systems, the information that will be obtained may be of value in other branches of science, for example in engineering where coupling of non-linear oscillators may be important. The research will involve graduate student and postdoctoral researchers who will receive excellent training beneficial to their future careers in industry, government or academic research. This work is interdisciplinary in nature and is supported in part by the Office of Multidisciplinary Activities in the Mathematical and Physics Sciences Directorate at NSF. ***
