Controlling the functionality of quantum materials by light

Prof.  Daniele Fausti (University of Trieste and University of Erlangen Nuremberg)

Abstract

The physical properties of many complex Quantum Materials (QM), like transition metal oxides, are the results of a complex interplay among electrons, phonons, and magnons. This complexity makes the properties of QM highly susceptible to external factors such as pressure, doping, magnetic fields, or temperature. This leads to the intricate phase diagrams found in many families of compounds and, in turn, provides the means to switch between completely different macroscopic functionalities by a fine tuneing of “control parameters”, such as temperature or pressure. The same susceptibility also renders QM an ideal platform for designing experiments where tailored electromagnetic fields interacting with matter can lead to the emergence on ultrafast timescales of novel, occasionally exotic, physical properties. This aspect has been explored in time domain studies [1] and has led to different proofs that ultrashort mid-IR light pulses can “force” the formation of quantum coherent states in matter. Those findings disclose a new regime of physics where photo- excitation can be used to dynamically “sustain” quantum coherence, thermodynamic-limits may be bridged and quantum effects can, in principle, appear at ambient temperatures, where thermal fluctuations normally inhibits them at equilibrium. In this presentation, I will review our recent results in archetypal strongly correlated cuprate superconductors and demonstrate the feasibility of a light-based control of quantum phases in real materials [2,3,4]. I will then introduce our new approaches to time domain spectroscopy going beyond mean photon number observables [5-10] and show that the statistical features of light can provide information on superconducting fluctuations beyond standard linear and non-linear optical spectroscopies [11]. Finally, I will elaborate on our current research effort to use cavity electrodynamics to control the onset of quantum coherent states in complex materials [12].

Zoom link:

https://zoom.us/j/99542736244?pwd=U1YwVVZTVWtOOXE3QjFJbWlrQ1AyQT09