Quantum Phase Transitions and Effects of Dissipation in Low-Dimensional Superconductors

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This individual investigator award will support the continuation of a project to study the dynamics of Quantum Phase Transitions (QPT) and in particular the effects of dissipation. During the past three years this program has been a major source for new experimental data and re-analyses of data in other systems, that point to the occurrence of phase separation and the existence of "metallic" phases in two-dimensional Superconductor-Insulator-Transition (SIT) films. Through new choices of model-system materials the current project will try to complete the true phase diagram of two-dimensional SIT in the presence of dissipation. In particular it will emphasize the electronic microstructure of the SIT system near the transition, the issue of phase separation, and the possible sources of dissipation. Obtaining more insight into the SIT with dissipation problem will shed light on other outstanding problems such as high-Tc superconductivity, colossal magnetoresistance and strongly correlated magnets. Through graduate students thesis work, undergraduate students involvement, and a new course on quantum coherence and dissipation to be designed by the PI, the project will continue to have a strong educational component.%%%Many physical systems, although very different in nature, can be described by similar physical principles. Thus, finding appropriate model systems for outstanding physics problems, and in particular problems that relate to both, basic science and applications is of fundamental importance. The problem of Superconductor-Insulator-Transition (SIT) in two dimensional films has been shown to exhibit physics relevant to the understanding of high-Tc superconductors (important for superconductive electronics and low-loss conductors for power handling,) as well as to two-dimensional electron gas systems (important for electronic-device applications in the quantum limit.) The present program extends our study of SIT systems to include more materials (i.e. extending parameter space of the model system) and design new probes to study the system at the microscopic scale. The program will continue to have a strong educational component to it through graduate students thesis work, undergraduate students involvement, and a new course on quantum coherence and dissipation to be designed by the PI.***