EAGER: SUPER: Coupling High-Energy Phonons into High-Tc Superconductors

Yale University, New Haven CT

Investigators

Abstract

NONTECHNICAL SUMMARY This EAGER project supports research and education activities to create a more robust superconductor with the help from light elements on the periodic table. Superconductivity - the lossless transmission of electricity in a solid-state material - most commonly relies on the formation of electron pairs due to an attraction provided by atomic vibrations. In most bulk superconductors, this vibration is too slow to maintain the electron pairing at everyday temperatures - lots of electrons with little glue. Compounds with light elements naturally contain the fastest atomic vibrations, but the highly vibrative nature also prevents the formation of a stable, compact crystal lattice that can conduct electricity - a lot of glue with few electrons. The main goal of this EAGER project is to use advanced synthesis to create a stable and compact crystal lattice enriched with light elements such as hydrogen, carbon and lithium. This would provide both sufficient electrons and pairing glue simultaneously, therefore strengthening superconductivity to weather ambient conditions. One way is to create preferred light-element occupation sites in existing layered bulk superconductors via selected large molecule intercalation. The other is to grow high-temperature superconductors on light-element substrates layer-by-layer. Both methods are aimed to create atomic confinement of light elements in proximity to pre-existing superconducting electrons. This project supports the education of three graduate students, cohesively working across the full cycle of synthesis, characterization and theory. The intuitive and generic conceptual approach is to be developed as an important teaching example in upper division college physics curriculum. This project also offers a demonstration of the modern materials design pipeline, which will be used to develop research projects of undergraduate and public-school students. TECHNICAL SUMMARY This EAGER project supports research and education activities that investigate the possible use of high-frequency phonons from light elements to boost superconductivity in existing high-temperature superconductors. In particular, lithium and hydrogen rich compounds will be used to boost the transition temperature and critical supercurrent of copper- and iron-based superconductors. Unlike traditional methods, which often result in uncontrolled light element placement and structural damage to the treated material, this project aims to better regulate the process with i) a dopant-assisted light-element intercalation in bulk materials, and ii) light element substrate-enhanced superconductivity in thin film superconductors. The first method creates preferred light-element occupation sites in existing layered bulk superconductors via selected large molecule intercalation. The other method aims to grow high-temperature superconductors on light-element substrates layer-by-layer. In practice, via both approaches, a highly ordered solid state structure with enriched light element composition is to be created and stabilized under ambient conditions. This project examines the effectiveness of the general framework of “hybrid” superconductivity, achieved via targeted combination of favorable superconducting contributors - strong pairing and strong conduction. The proposed bulk and thin-film synthesis complement each other in terms of tunability and applicable characterization methods. This project supports the education of three graduate students, cohesively working across the full cycle of synthesis, characterization and theory. The intuitive and generic conceptual approach is to be developed as an important teaching example in upper division college physics curriculum. This project also offers a demonstration of the modern materials design pipeline, which will be used to develop research projects of undergraduate and public-school students. 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.