The exchange of angular momentum among electron spin, orbital, and lattice degrees of freedom governs the topology, transport, and magnetization dynamics of magnetic materials. Probing the interactions among magnons, phonons, and electron orbital angular momentum has become a global focus in condensed-matter physics, yet the underlying mechanisms—operating on nanometer and femtosecond–nanosecond scales and under non-equilibrium conditions, such as applied current/voltage, optical excitation, and thermal gradients—are difficult to probe with conventional static measurements. To address this challenge, our Center for Quantum Dynamics of Angular-Momentum advances operando imaging that synchronizes stimuli and responses to achieve real-time spatiotemporal resolution across multiple platforms. This overview introduces five representative operando instruments developed and deployed at our Center: (i) scanning tunneling microscopy (STM), (ii) time resolved magneto-optic Kerr effect (MOKE) microscopy/spectroscopy, (iii) magnetic force microscopy (MFM), and (iv) diamond nitrogen-vacancy (NV) center quantum microscopy, (v) scanning electron microscopy with polarization analysis (SEMPA), providing complementary access to angular momentum dynamics in solid state systems.
Kim et al. (Fri,) studied this question.