https://umich.zoom.us/j/94692610056

The development of methods for generation of strong terahertz-frequency electromagnetic fields has enabled the advance of nonlinear THz spectroscopy and 2-dimensional THz spectroscopy of collective and molecular degrees of freedom. These methods have revealed multiple-quantum coherences and correlations among modes ranging from gas-phase molecular rotations to lattice vibrations (optical phonons) in quantum paraelectric crystals to spin waves (magnons) in canted antiferromagnetic systems. Recent results will be reviewed and will segue from nonlinear THz spectroscopy to nonlinear THz control over material structure and behavior. Structural and electronic phase transitions have been induced by THz fields, yielding transient or long-lived phases whose formation dynamics have been monitored using THz, optical, and x-ray probes. Finally, the prospects for excitation of multiple modes including acoustic and optical phonons, magnons, and low-frequency electronic responses in order to reveal their interactions and to guide materials through complex multiphase landscapes will be discussed.