LAUSR

Attosecond interferometry relies on the application of a train of attosecond extreme-ultraviolet (XUV) pulses and a synchronized low-intensity infrared (IR) field to measure the dynamics of photoemission via the interference signal in the spectrum of emitted electrons. So far, all condensed-phase experiments relying on this technique have investigated metallic, i.e. nontransparent, systems and have revealed the importance of transport and final-state effects. Here, we demonstrate the existence of a nonlocal mechanism of attosecond interferometry general to all condensed-matter systems and particularly important for those that are transparent to the IR. Key to the process is that, after XUV absorption, additional emission pathways result from the absorption or emission of an IR photon at remote positions due to the potential of neighboring atoms (or molecules). By solving the time-dependent Schrödinger equation (TDSE) in one dimension, we show that interference of the resulting local and remote pathways leads to a mapping of the atomic or molecular environment onto the attosecond interference signal. We derive an analytical theory for the local and remote pathways as well as the resulting response and find excellent agreement with the TDSE. Our analytical theory shows that the nonlocal mechanism generally encodes both mean-free paths and scattering delays into the experimental observables. We generalize the analytical theory to the case of multiple collisions and study the effect of path-length distributions typical of electron scattering in condensed matter.