TopQMat · Nonequilibrium Topological States in Quantum Materials

Discovering routes to guide materials into desired phases through so-called topological phase transitions is one of the goals in modern condensed matter physics. The properties and invariants of topological materials are strongly related to the existence or breaking of certain symmetries, and by using external perturbations, topological phase transitions can be induced. However, ultrafast nonequilibrium processes hold the potential to revolutionise the manipulation of topology in quantum materials.TopQMat is an ambitious project which aims to drive ultrafast topological phase transitions in quantum materials and measure the associated modification of topological character of their electronic band structure with angle resolved photoemission spectroscopy. More specifically, the focus is (i) to develope innovative measurement techniques to probe the topological character of energy bands (Berry curvature, orbital pseudospin texture, Bloch wavefunction) using time-, angle-, and polarization-resolved multidimensional photoemission spectroscopy, under non-equilibrium conditions, (ii) throught femtosecond laser pulses, employ impulsive excitation of coherent phonon modes to periodically alter the symmetry of the lattice, to induce ultrafast out-of-equilibrium topological phase transition, and (iii) study and induce Floquet-Bloch engineering of topological states in optically driven quantum materials, aiming to identify the conditions and microscopic mechanisms that enable their creation with non-trivial topological characteristics.This project will push the boundaries of current knowledge on topological matter and ARPES measurements.These aspects are crucial for understanding the behaviour of materials and their electronic properties. By employing cutting-edge techniques and methodologies the project seeks to unravel the nature of local topology in the electronic structure during out-of-equilibrium topological phase transitions.