The scaling analysis of voltage vs. current curves has been an invaluable tool in the study of the normal-superconducting phase transition. However, recent work has shown that the conventional application of this tool is too flexible to uniquely determine the critical parameters, and that extrinsic effects can obscure or destroy the phase transition. With these caveats known, we can more carefully apply the tools to determine the critical parameters of the normal-superconducting phase transition, both in a field and in zero field. This individual investigator award supports a project that will apply these tools to a novel material: the electron-doped superconductor Pr2-xCexCuO4-y (PCCO). This project will study the critical dynamics of PCCO as a function of doping and field. PCCO has displayed an array of interesting behaviors, such as d- to s-wave pairing, a transition to an insulating state, and a quantum critical point. Any and all of these phenomena may affect the dynamics of the phase transition. This project will add to our understanding of the phase transition in electron-doped superconductors, and in particular, explain why the electron-doped materials behave so differently from their hole-doped counterparts. This project will also train undergraduate students in experimental and low-temperature physics and will contribute to an existing outreach program with local public schools to encourage broader education in science.
High-temperature superconductors, discovered more than two decades ago, still hold great promise and great challenges. The promise lies in the hope of eventually making superconductors with much higher transition temperatures, and the challenges lie in the fact that we do not, even two decades later, fully understand how or why these materials superconduct. It is known that superconductors can be made, or "doped," with two types of electric charge carriers: electrons, or the space left by the lack of an electron, called a "hole." There is no theoretical difference between electrons and holes as charge carriers, and yet, hole-doped superconductors have much higher transition temperatures and are different in several other ways than their theoretically identical companions, electron-doped superconductors. This individual investigator award supports a project that will study how novel electron-doped materials become superconducting, in the hopes of understanding the underlying mechanism that creates superconductivity in these materials. The proposed studies will add to the knowledge of high-temperature superconductors and held fulfill the promise of attaining higher transition temperatures. This project will also train undergraduate students in state-of-the-art film growth, characterization, and measurement techniques, and will contribute to broader educational goals by adding science outreach to local elementary schools and adding low-temperature physics to advanced laboratory courses.
