“Optical control and quasiparticle witnessing in strongly correlated electron systems”

Daniele FAUSTI

University of Trieste

The prospect of “forcing” the formation of quantum coherent states in matter, by means of pulsed electromagnetic fields, discloses a new regime of physics where thermodynamic limits can be bridged and quantum effects can, in principle, appear at ambient temperatures. In this presentation I will introduce the field of optical control of correlated electron systems. I will focus on the possibility of coherently driving low-lying excitations of quantum many body systems making light-based control of quantum phases in real materials feasible. I will review the recent results in archetypal strongly correlated cuprate superconductors and introduce our new approach to go beyond mean photon number observables. I will show that the measurement of multimode correlations of classical and quantum nature can provide a richer statistical information than standard linear and non-linear optical spectroscopies. This will potentially uncover with unprecedented detail the evolution and properties of light-induced transient states of matter.

“Femtosecond X-ray spectroscopy and scattering : combining local and global observables for chemical dynamics studies”

Wojciech Gawelda

Europe-an XFEL, 22869 Schenefeld GERMANY

Faculty of Physics, Adam Mickiewicz University,Poznan, Poland

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“Study of Magnetoelectric using Soft X-ray Scattering”

Paul Steadman

Diamond Light Source Ltd

Harwell Science and Innovation Campus

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Spherical cavity optomagnonics

Arnaud Gloppe

Research Center for Advanced Science and Technology – The University of Tokyo (Japan)

Macroscopic magnetically ordered structures, such as Yttrium Iron Garnet (YIG) millimetric spheres, are solid supports of extended collective spin excitations, magnons, that can be cooled down to their quantum ground state and coherently coupled to a superconducting quantum bit through a microwave cavity [1]. The coherent optical control of magnons in the quantum regime would enable the efficient transduction of optical and microwave photons [2], opening the way to quantum telecommunications between superconducting quantum computers, as well as quantum-noise limited microwave amplifiers.

The study of the interactions of magnons and photons in an optical cavity – or cavity optomagnonics, in a solid-state matrix has emerged recently with the first observations of magnon-induced Brillouin light scattering involving magnons in the uniform magnetization precession mode (so-called “Kittel mode”) and whispering gallery mode photons hosted by a YIG sphere [3]. Higher-order spin-wave modes, with a variety of orbital angular momentum and spin textures, extend the richness of this hybrid system. We will discuss the first experimental measurements of Brillouin light scattering due to magnetostatic modes beyond the Kittel mode, giving access to a deeper understanding of the mechanisms ruling spherical optomagnonics systems. We will reveal a non-reciprocal behavior of the light scattering, function of the azimuthal dependence of the involved spin-wave mode, related to the conservation of orbital angular momentum in the system [4,5]. Finally, we will present a method to image the spin-wave modes structures in objects with this geometry [6], required to robustly identify higher-order modes, paving the way to the systematic investigation of the optomagnonic interaction.