Novel schemes for ultrafast manipulation of quantum materials

Many materials of great scientific and technological interest have an intrinsically multi-orbital electronic structure which leads to a variety of remarkable phenomena, such as metal-to-insulator phase transitions, superconductivity, exotic magnetic phases and multiferroicity. The goal of my project is to use ultrafast spectroscopy to investigate the transient properties of multi-band correlated materials, which constitute a wide class of solid state systems where multiple bands of different orbital origin determine the low-energy electronic properties. The possibility of using ultrashort light pulses to modify the equilibrium population within the bands provides a new interesting tool to manipulate the properties of materials with light. During the project I will mainly focus on the following materials: • iron-based superconductors, where the multiband nature is related to the five d-orbitals of the Fe atoms • transition-metal oxides (e.g. LaVO3 and V2O3), in which both the transition metal oxide 3d orbitals and the O-2p orbitals contribute to the conduction and valence bands. The ultrafast dynamics, after the sudden excitation with light pulses, will be measured via three different experimental techniques: • Conventional pump-probe. • Coherent-control experiment in which the pump will be constituted by the coherent overlap between a fundamental radiation pulse and its second harmonics. The interference between the electronic transitions driven by the two pulses is expected to give rise to a change of the band population that is selective in momentum space. • Two-dimensional spectroscopy, a non-linear technique based on the use of two different coherent pump pulses at the same frequency. This technique allows to investigate the quantum-decoherence of the macroscopic polarisability, thus providing important information about the scattering processes in the materials.

Publication year:2022

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