EXCITE · Exposing Hidden Electronic Configurations in Atomically Thin Superstructures with Extreme Light

Light-induced phase transitions in solids present a tantalizing opportunity for controlling the constituents of matter. An intense optical excitation with a duration on the order of femtoseconds can trigger nonthermal electronic and structural configurations, switching the excited material into a hidden phase that may be exploited to realize new technologies such as ultrafast memory devices. A general picture of the microscopic processes underpinning hidden phases has not been established. Their existence has therefore only been exposed in a handful of systems, presenting a major obstacle for achieving on-demand quantum materials with light.Drawing inspiration from these unique systems, I hypothesize that materials with a strongly correlated phase that is pinned by a two-dimensional superstructure provide a trajectory to a light-induced hidden phase. The objectives of EXCITE are (A) to establish the experimental parameter space to determine the electronic structure of hidden phases in bulk and single-layer correlated transition metal dichalcogenides, (B) to demonstrate the existence of hidden phases in optically excited moiré superstructures that simulate strongly correlated behavior and (C) to exploit the wide tunability of these systems in order to disentangle the general microscopic degrees of freedom that govern the trajectory into a hidden phase.The objectives will be accomplished by establishing a state-of-the-art experiment to optically excite in situ prepared materials and probe their electronic structure during phase transitions with nanoscale spatial resolution and femtosecond time resolution. These ground-breaking capabilities will be realized by integrating a high-power laser system with my new synchrotron beamline for nanoscale photoemission spectroscopy (nanoARPES) at the ASTRID2 light source, Aarhus University. My experiments will enable me to critically assess basic assumptions in the field and move the boundaries of ultrafast science.