Ultrafast topological engineering of quantum materials

Introduction

Topological phases of matter emerge from the interplay between broken symmetries and many-body physics and exhibit many fascinating quantum phenomena. Ultrafast switching between different topological phases using light pulses holds the promise for disruptive optoelectronic functionalities, like dissipationless and fault-tolerant logical operations.

Challenge

However, the lack of proper observables being simultaneously sensitive to the local (in momentum-space) topology of the band structure and compatible with time-resolved measurements prevents the real-time monitoring of ultrafast non-equilibrium topological phase transitions.

Methodology

I will address this fundamental challenge by introducing innovative control and measurement methodologies using tailored light pulses in time-, angle-, and polarization-resolved extreme ultraviolet photoemission spectroscopy. This approach will enable the following:

1. Follow the ultrafast evolution of the electronic band structure’s local topology in photoexcited quantum materials.
2. Represent a major advance in photoemission spectroscopy by moving from band structure mapping to accessing the dynamical evolution of the Bloch wavefunction of solids.

Investigation

I will use these novel time- and quantum-state-resolved dichroic observables to investigate the rich non-equilibrium physics underlying ultrafast topological phase transitions occurring on various timescales following impulsive optical excitation using shaped pump pulses:

i) During the formation of hybrid light-matter (Floquet-Bloch) states,
ii) Upon the transient modification of electronic correlations,
iii) Following the excitation of coherent phonon modes.

Impact

UTOPIQ will deliver a dramatically improved understanding of the interplay between the non-equilibrium behaviour and non-trivial topology in photoexcited quantum materials, while further representing a decisive step towards the development of the field of ultrafast ‘on demand’ topology.