Ultrafast spin-phonon coupling and twisted nonlinear optics in vdW materials

Van der Waals (vdW) materials hold immense promise for new nanotechnologies. However, more insight into their behavior under non-equilibrium conditions on femtosecond time scales and their support of exotic nonlinear processes is needed. In this talk, we will first discuss our recent studies of ultrafast lattice and spin dynamics in vdW magnets. Here, we uncover unusually strong transient spin-phonon coupling, manifesting as pump helicity-dependencies and dynamic magnetostriction-driven stiffening of coherent phonon modes. In both these cases, these phenomena originate from the pronounced modulation of exchange interactions through the distortion of the lattice. We will then turn to nonlinear optical processes, namely harmonic conversion and optical parametric amplification driven by twisted light. Here, we show both the efficient harmonic scaling of orbital angular momentum and the free tuning of wavelength and topological charge of vortex beams, both supported by atomically thin semiconductors. Our work points to new ways to exploit femtosecond and structured illumination to extend the versatility of vdW materials in the pursuit of new spintronic and optoelectronic applications.