1. Center for Functional Nanomaterials Seminar

    "Uncovering Ultrafast Magnetic Dynamics and Collective Excitations in Quantum Materials"

    Presented by Prashant Padmanabhan, Center for Integrated Nanotechnologies, Los Alamos National Laboratory

    Friday, September 11, 2020, 2 pm
    ZoomGov - https://bnl.zoomgov.com/j/1604642090

    Hosted by: Mircea Cotlet

    The first demonstration of transient demagnetization after femtosecond optical excitation was a seminal achievement in condensed matter physics that led to the birth of the field of ultrafast magnetism. Today, we continue to work towards unravelling the nature of the mechanisms that underlie these processes and develop methods for exploiting them to harness new magnetic phenomena. With the recent emergence of quantum material systems hosting novel intrinsic magnetic order, we now have an exciting new playground to study the transient interactions between photons and spin excitations and phases. In this talk, I will discuss our efforts in using such systems to both control the properties of electromagnetic radiation and coherently drive collective magnetic phenomena with light, focusing on three examples. First, I will highlight our efforts aimed at manipulating terahertz pulses by leveraging magneto-plasmonic resonances in micro-structured graphene. I will then examine how light can be used to directly manipulate magnetic order. Here, ultrafast optical quenching of magneto-crystalline anisotropy in the multiferroic skyrmion-host GaV4S8 can drive coherent collective breathing and rotational skyrmion lattice excitations. Finally, I will discuss our recent work involving the ferromagnetic van der Waals crystal CrI3. Our experiments shed light on the nature of angular momentum transfer in this material and reveal a strong coupling between the spin and lattice degrees of freedom. This manifests as coherent spin-coupled phonons whose vibrational amplitude is highly sensitive to the helicity of the driving optical pulse. Together, these three examples codify the immense promise that ultrafast optics holds in understanding and utilizing the novel magnetic properties of quantum materials. Moreover, they point a path towards generating dynamic states with light that may be the key to unlocking the next generation of high-speed memory and nanoscale magneto-optical technology.