Superconducting and Metal-Insulator Transitions in Quasi-Two-Dimensional Strongly Correlated Materials

Florida State University, Tallahassee FL

Investigators

Abstract

NONTECHNICAL: Electronic properties of many new materials with potentially great technological importance are dominated by interactions among charge carriers. Those correlations give rise to a variety of phenomena, including the emergence of novel states of matter and transitions between different phases, such as metal to insulator or superconductor to normal. However, microscopic mechanisms underlying these transitions and the nature of various phases in such strongly correlated systems are not well understood. This research addresses fundamental questions about superconducting and metal-insulator transitions in two classes of layered, strongly correlated materials, copper-oxide high-temperature superconductors and a new series of organic systems, by performing measurements of charge transport over a wide range of temperatures and magnetic fields. The results of this project are crucial for understanding of strongly correlated materials, which will benefit society by ultimately influencing the development of science and technology. A key component of the project is education and training of graduate students for future careers in academia, national laboratories, and industry. It also incorporates various activities to broaden the participation of underrepresented groups in the areas of science, technology, engineering, and mathematics, outreach to general public, and impact on research infrastructure. TECHNICAL: This project addresses several fundamental questions in the physics of strongly correlated materials, such as unconventional superconductivity and the Mott metal-insulator transition in quasi-two-dimensional systems. Since anomalous transport properties are one of the key characteristics of strongly correlated materials, experiments involve electrical transport, including time-resolved protocols. Studies focus on two classes of quasi-two-dimensional systems, cuprates and newly synthesized substitutional series of quasi-two-dimensional organics. In both cases, unconventional superconductivity emerges as a result of tuning through the Mott transition by varying doping or chemical pressure, respectively. In cuprates, the goal is to probe the destruction of superconductivity by high magnetic fields and to clarify the respective roles of spin and charge orders, disorder, and quantum phase fluctuations, as a function of doping. In organics, the focus is on understanding unconventional superconductivity by exploring both thermal and magnetic-field-tuned superconducting transitions. In addition, the Mott metal-insulator transition and the role of spin liquid excitations are probed using time-resolved techniques. The knowledge gained from this project is essential for further development of condensed matter physics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.