Designing crystal structures with light: the dawn of out-of-equilibrium matter

An emering frontier of condensed matter, unifying topological, strongly interacting, mechanical and chemical properties of solids lies in the response of materials to light.

In this talk, I'll present remarkable consequences of light-matter interaction in solids: new, out-of-equilibrium crystalline phases that oscillate in time. These states are generated through parametric excitation and are the result of coherent energy down-conversion in cystalline systems, unlike normal dissipation or heat generation we are familiar with.

I will examine the various means by which such order can be observed: from phonons in crystals, to Goldstone modes of symmetry-broken interacting phases. I will review the difference between continuous-wave and pulsed excitations on materials, revealing that even short (femtosecond) excitations can result in order that continues for longer -- even orders of magnitude longer.

I will explain the remarkable stability of these states to external noise, what we woudl normally call "temperature". I will explain that the fact that system is driven permits a "cooling" effect on the emergent order at finite frequency, creating a new paradigm of structures that are immune to perturbations with tantalizing future applications.