LASSP & AEP Seminar: Nuh Gedik (MIT)

Description

Terahertz field induced metastable magnetization in a van der Waals antiferromagnet

Controlling the functional properties of quantum materials with light has emerged as a frontier of condensed matter physics, leading to discoveries of various light-induced phases of matter, such as superconductivity, ferroelectricity, magnetism, and charge density waves. However, in most cases, the photoinduced phases return to equilibrium on ultrafast timescales after the light is turned off, limiting their practical applications. In this study, we use intense terahertz pulses to induce a metastable magnetization with a remarkably long lifetime of over 2.5 milliseconds in a van der Waals antiferromagnet, FePS3. The metastable state becomes increasingly robust as the temperature approaches the transition point, suggesting a significant role played by critical fluctuations in facilitating extended lifetimes. By combining first principles calculations with classical Monte Carlo and spin dynamics simulations, we find that the displacement of a specific phonon mode modulates the exchange couplings in a manner that favors a ground state with finite magnetization close to the Néel temperature. This analysis also clarifies how critical fluctuations amplify the magnitude and the lifetime of the new magnetic state. Our discovery demonstrates the efficient manipulation of the magnetic ground state in layered magnets through non-thermal pathways using terahertz light, and establishes the regions near critical points with enhanced fluctuations as promising areas to search for metastable hidden quantum states.
 

Bio:
Nuh Gedik joined MIT Physics Department as an assistant professor in January 2008. He received his B.S. in physics in 1998 from Bogazici University, Istanbul, Turkey and his Ph.D in physics in 2004 from University of California, Berkeley.

After his Ph.D, he moved to Caltech where he worked as a postdoctoral scholar until January 2008. His awards include National Science Foundation CAREER Award, Department of Energy Early Career Award, Sloan fellowship, DARPA Young Faculty Award and Moore Experimental Investigator award. He was promoted to Full Professor of Physics in 2018.

Professor Gedik’s research centers on investigating quantum materials by using advanced optical and electron based spectroscopies. Quantum materials are systems in which strong correlations lead to fascinating emergent phenomena such as high temperature superconductivity or colossal magnetoresistance. Despite intense research for decades, uncovering the physics of these materials with conventional techniques has been very difficult. This is mainly because different degrees of freedoms (i.e. charge, spin and lattice) are strongly coupled in these systems and interplay between them is responsible for many of their exciting properties. Gedik group develops novel time-resolved techniques to selectively probe dynamics of charge, spin and lattice excitations with unprecedented time, momentum and energy resolutions. Material systems of interest include topological insulators, high temperature superconductors and atomically layered materials.