EAGER: SUPER: Light-Induced Room-Temperature Superconductivity at Light Pressure

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NONTECHNICAL SUMMARYThis EAGER award supports theoretical and experimental research, and education on using light to induce and probe superconductivity. In conventional superconductors at sufficiently low temperature, electrons form a collective quantum mechanical state with unusual properties including the ability to conduct electricity without resistance. Superconductivity typically often occurs under seemingly extreme conditions, appearing either at very low temperatures where some common gases are liquids or, as recently demonstrated for light-element hydrogen-based compounds, under very high pressures approaching those found deep in the core of planets. However, recent experimental advances in laser physics suggest that light, like pressure, can act as a kind of "knob" to control the electronic behavior of materials, suggesting a striking alternative possibility of attaining superconductivity at much higher temperatures or more modest pressures approaching ambient conditions. The central goal of this project is to leverage tailored irradiation with light to study and control electronic properties of superconducting compounds. While conventional superconductivity is well-studied in the steady state of equilibrium, the response of electrons in superconductors to strong external fields such as a light remains less understood and constitutes the main focus of this combined theoretical and experimental effort. This project involves the development of theoretical models to predict the response of light-element superconductors driven out of equilibrium by targeted excitation of crystal lattice vibrations. The PIs will focus on classes of carbon and hydrogen bearing materials known as fullerides and hydrides. A specific aim is to chart pathways to utilize these vibrational modes as a substitute for pressure, to drive transformations from an insulating or metallic states to a superconducting state. Experiments will be performed involving optical spectroscopy measurements as a function of time synchronized to the time the laser pulse hits the material. Understanding the responses could help guide theoretical modeling and help in the design of future generation of electronic devices. This project includes several activities beyond standard professorial classroom teaching and mentoring of postdocs and students. The PIs are working on new course development and new outreach methods that will be a broad introduction of quantum materials to the STEM students and the general public. Particularly, first-generation college undergraduates will be involved in research problem to give them a sense of modern research in superconducting quantum materials.TECHNICAL SUMMARYThis EAGER award focuses on the use of light to induce superconductivity in light-element quantum materials. While unconventional cuprate superconductors hold the record for highest superconducting transition temperature at ambient conditions, a series of recent experiments demonstrated high transition temperatures in light-element conventional superconductors. These range from the fullerides to hydrides with landmark near-room-temperature superconductivity under pressure. While superconductivity in these materials requires extremely high pressures, recently a series of seminal experiments on cuprates, organic charge-transfer salts, and hydrides suggest that irradiation with optical pulses can in principle provide an alternative way to induce long-lived superconducting signatures out of equilibrium.The goal of this project is to demonstrate theoretically and experimentally that light can effectively be a substitute in the role of external pressure and induce a non-equilibrium superconducting state at much reduced pressures and high temperatures. To this end, the PIs will perform theoretical modeling and optical-pump terahertz-probe experiments on two classes of compounds, the fullerides and hydrides. For the former, a key aim is the experimental demonstration and theoretical description of a light-induced insulator-superconductor transition in the Mott-Jahn-Teller insulator out of equilibrium and at elevated temperatures, with emphasis on mimicking the role of external pressure through selective optical excitation of phonons. For the latter, the PIs aim to demonstrate light induced superconductivity in hydrides under pressure. To achieve a controlled enhancement of electronic pairing, the PIs will investigate theoretically and experimentally, targeted excitation of the phonon spectrum in these materials and the role of anharmonicities.The success of this project will represent an advance in the understanding of quantum phases driven far out of equilibrium and may open new research directions towards achieving light-element superconductivity at ambient conditions. Educational contributions include the integration of teaching and learning activities that will enable K-12 students and the general public to see macroscopic quantum phenomena outside of research laboratories and to raise their awareness of the STEM fields involved. These activities include mentoring postdocs and first-generation college undergraduate students, as well as working with the Franklin Institute Science Museum to perform demos onsite and record the videos into interactive virtual learning programming for K-12 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.