Discovering light-induced phases by first-principles material design

ongoing

Ultrafast lasers sources open new perspectives in exploring broken symmetry phases as it becomes possible to promote a substantial number of electrons in excited states generating a thermalized electron-hole plasma and leading to reversible or irreversible phase transitions. Light-induced charge density waves, order-disorder transitions, melting, stabilization of topological phases and laser-tunable ferroelectricity have been demonstrated. Experiments are far ahead of theory as few (if any) of the demonstrated light-induced phenomena have been predicted by theory. DELIGHT aims to develop a theoretical strategy to predict and discover photoinduced phases in materials. To accomplish this goal, we will develop quantum-chemical and molecular dynamics schemes including the effect of the thermalized electron-hole plasma on the crystal potential and accounting for light-induced non-perturbative quantum anharmonicity. DELIGHT will answer these questions: which systems undergo light induced phase transitions ? Can we use light pulses to enhance or tune charge density wave, ferroelectric and magnetic critical temperatures, to generate new topological phases or to optimize the properties of thermoelectric materials ? Can we develop an inverse design strategy, namely given a target property, determine which material will have to be photoexcited and at which fluence to obtain it ? The proposal will impact chemistry, physics, energy and material engineering. It could lead, for example, to the development of devices with dynamical light switching on/off of magnetism or ferroelectricity, relevant for ultrafast memories, or to the stabilization of new thermoelectric compounds with photo-tunable thermal conductivity and figure of merit. DELIGHT will foster these and similar developments by implementing a fundamentally new and unique database of out-of-equilibrium accessible states of matter that will be a reference for future experiments.