CAREER: Ferroelectric and magneto-electric dynamics in multiferroics driven by intense terahertz pulses

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Non-technical Abstract: A compass needle shares an important property with the data-storage layer on your computer's hard drive - they are both magnetized, or ferromagnetic. Another property of matter that allows data storage is ferroelectric polarization. This research explores how materials that are both ferroelectric and ferromagnetic respond to intense terahertz-frequency electric fields. The goal is to establish the physics of the materials interaction with the terahertz electric field. One terahertz frequency is more than one hundred times faster than your computer processor speed. Thus, this research potentially enables much faster data writing and storage functionality compared with the technologies available today. This project also aims to educate the next generation of scientists and engineers and to broaden the participation of women and under-represented minorities in sciences. The planned activities enhance the Tulane Science Scholar Program, whose goal is to attract high school students with exceptional promise in science and mathematics into engineering disciplines. The participation of underrepresented minorities in science and engineering is promoted through summer undergraduate student research with participants recruited from local Historically Black Colleges and Universities (HBCUs) in New Orleans on paid summer assistantships. The participation of women in sciences is promoted by the GIST (Girls in STEM at Tulane) program that provides middle-school girls with the opportunity to meet and work with women role models in science. Technical Abstract: This project targets a new frontier in technologically advanced ferroelectrics and multiferroics by focusing on ferroelectric and magnetoelectric dynamics driven by intense terahertz pulses, where both spin and lattice are resonantly excited. The goal is to discover the new physics that emerges when the coupled spin and lattice motion is coherently driven in the very large amplitude regime. It is hypothesized that the terahertz-driven dynamic ferroelectric and magnetic responses can approach in magnitude the responses induced by static electric fields and allow domain manipulation. Terahertz pulses with peak electric field exceeding 100 kV/cm are used to coherently excite the large-amplitude ionic motion along the ferroelectric phonon coordinates. The spin dynamics is excited via the magneto-electric coupling of spin to the lattice motion. The response of the order parameters is probed using terahertz and optical probe pulses. This work aims to create new knowledge of the nonequilibrium response of matter to intense terahertz pulses and to provide guidance for the design of future terahertz-frequency magneto-electric and data storage devices.