The Ultrafast Einstein-de Haas Effect
Prof. Dr. Steven Johnson (ETH Zürich Institute for Quantum Electronics)

The original experiments showing what is now called the Einstein-de Haas effect were a critical demonstration in early modern physics of the equivalence of angular momentum in electronic spins and mechanical angular momentum. Here I discuss a recent experiment where we investigate using femtosecond x-ray diffraction the dynamics of the Einstein-de Haas effect on picosecond time scales, along the way showing definitively that the long-studied but poorly understood phenomenon of “ultrafast demagetisation” in ferromagnetic iron involves a sub-picosecond time scale transfer of angular momentum from the spin system to the lattice.