APhMS Special Seminar

**Refreshments outside Noyes at 10:45am

Abstract

I will discuss how coherent electromagnetic radiation, when tuned to drive collective modes in quantum materials, can be used to induce unexpected dynamical phases. The core idea is that when uncoupled normal modes are driven nonlinearly, subdominant mode interactions that do not influence the equilibrium physics become important. Such nonlinear phononics/magnonics/plasmonics etch. Takes inspiration from nonlinear optics to coherently control materials function. An illustrative set of examples will be discussed for the nonlinear control of the crystal lattice, which is used to induce magnetic order in paramagnetic materials, ferroelectricity in paraelectrics and non-equilibrium superconductivity at high temperatures. These studies open up new directions in fundamental research, but also exposes a set of phenomena that will inevitably be encountered if one wishes to use quantum materials in ultra-high bit-rate applications.

More about the Speaker:

Andrea Cavalleri is the founding director of the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg (Germany) and a professor of Physics at the University of Oxford (UK). He received a PhD in electrical engineering from the University of Pavia (Italy) and held postgraduate and research staff positions at the University of California San Diego, and at the Lawrence Berkeley National Laboratory. He joined the Oxford faculty in 2005 and the Max Planck Society in 2008.

He is best known for his experimental studies of the photo-induced phase transition in functional complex materials. In his work, he has shown that through coherent optical control, one can achieve non-equilibrium functional states like superconductivity, ferroelectricity or ferromagnetism, at temperatures far above the equilibrium transition temperature, and can switch between them at ultrahigh speeds. He has also been a major driver in the development of ultrafast X-ray techniques since their inception in the late 1990s through their modern incarnation at X-ray Free Electron Lasers.

Cavalleri is a recipient of the 2004 European Young Investigator Award, of the 2015 Max Born Medal from the IoP and the DFG, of the 2015 Dannie Heineman Prize, the 2018 Isakson Prize from the American Physical Society and the 2024 European Physics Prize. He is an elected fellow of the APS, of the AAAS, and of the IoP, and a Member of the Academia Europaea.