SPINFIELD · Controlling spin angular momentum with the field of light

Short pulses of light allow controlling electrons in solids with superb precision and outstanding speed, now reaching the sub-femtosecond timescale. Yet, our ability to act on the angular momentum of materials at these ultrafast time scales is surprisingly close to inexistent. This is because very little is known about direct, first-order coherent interactions between the electromagnetic field of light and angular momentum. Predictions show that these interactions are extraordinarily complex and comprise components of fundamentally different nature – originating from quantum many-body effects, relativistic quantum electrodynamics, or symmetry breaking. These coherent phenomena, however, have yet to be directly captured. The proposed research aims at unveiling this class of direct light-spin interactions for the first time. My strategy relies on the use of the shortest pulses of light available today – attosecond pulses – employed to probe systems which selectively enhance different components of the coherent response. We will establish spectroscopic schemes building upon mature state-of-the-art attosecond technology, providing clear-cut evidence of phenomena which are in the blind spot of current approaches. Two control scenarios will be explored – in the first one, ultrashort pulses will redistribute angular momentum among the system constituents, on sub-femtosecond timescales. In the second, the spin angular momentum of light pulses itself will be imparted to matter, thereby coherently controlling the magnetic and topological properties of materials. We aim to answer key fundamental questions reaching across several disciplines of physics. Because spin angular momentum in solids is intimately related to magnetism and topology, SPINFIELD will also provide a decisive blueprint guiding the design of a new generation of devices that can be optically controlled and switched at unrivaled speeds.