Discovering light-induced phases by first-principles material design

Introduction

Ultrafast laser 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.

Project Goals

DELIGHT aims to develop a theoretical strategy to predict and discover photoinduced phases in materials. To accomplish this goal, we will:

1. Develop quantum-chemical and molecular dynamics schemes.
2. Include the effect of the thermalized electron-hole plasma on the crystal potential.
3. Account for light-induced non-perturbative quantum anharmonicity.

Research Questions

DELIGHT will answer the following 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?
• Can we generate new topological phases or 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?

Impact

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.
• 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.