CAREER: Probing Terahertz-driven Non-equilibrium Phenomena in Superconductors

About This Grant

Non-technical abstract Superconductivity is a phenomenon in which a material’s electrical resistivity disappears. The remarkable property of the zero resistance has enabled many important applications, such as generating powerful magnetic fields for maglev trains and MRI machines. Moreover, superconductors hold significant promise for quantum computing, a technology that can drastically reduce the time required to solve specific computational problems. As such, advancing our understanding and control of superconductivity remains a cornerstone of condensed matter physics. Recent advances in laser technology have opened exciting possibilities for manipulating superconductivity on ultrafast timescales using light. However, many fundamental questions about superconductivity remain unanswered due to a lack of necessary tools capable of probing the underlying properties directly. This project seeks to address these challenges by developing and applying innovative ultrafast spectroscopic techniques to explore non-equilibrium superconductivity. In addition to its scientific goals, the project includes a robust educational component. It aims to enhance the curriculum in ultrafast and nonlinear optics, provide mentorship opportunities for graduate and undergraduate students, and conduct outreach activities with local schools in the New York area to inspire the next generation of scientists and engineers. Technical abstract This project investigates light-driven non-equilibrium dynamics in various superconductors by focusing on the terahertz (THz) frequency range, a natural energy scale of superconducting gap energy. Thus, THz driving can avoid injecting excess heat and lead to unprecedented phenomena, which provide unique properties of superconductivity that are unreachable by frequently used near-infrared excitation. Nevertheless, the study of non-equilibrium superconductivity remains in its infancy due to the lack of appropriate probes of superconductivity on the ultrafast time scale of a few picoseconds. The project will investigate THz-driven collective excitations of superconducting order parameters that can provide unique information, including couplings between two superconducting order parameters and pairing symmetry. This project employs newly developed THz multidimensional coherent spectroscopy for this goal. The project also aims to manipulate superconductivity optically, including its phase coherence and topology, using the recently proposed Floquet engineering. Raman spectroscopy is combined with THz driving to investigate the superconducting order parameter. The innovative spectroscopic techniques developed here are broadly applicable to diverse quantum materials, including frustrated magnets, topological insulators, and Moiré materials. The techniques establish a foundation for exploring light-driven non-equilibrium phenomena, potentially leading to groundbreaking discoveries in 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.