We aim to establish: 1) novel, highly efficient, all-optical ways of enantio-discrimination, 2) enantio-resolved movies of chiral electronic dynamics, 3) chiral topological light – a new tool for chiral interactions, and 4) bridges between light-driven electron dynamics in chiral gases and topological effects in solids, with the goal of establishing new efficient and robust enantio-sensitive observables, where efficiency comes from local chirality and robustness comes from topological concepts.
1) We have established two new efficient methods of enantio-discrimination based on local chirality: Enantio-sensitive Free Induction Decay (Khokhlova et al, Science Advances 2022) and Enantio-sensitive Sum-Frequency Generation (Vogwell et al, Science Advances 2023). Sum frequency generation (SFG) is an example of non-invasive and versatile technique, but its application to chiral sensing was limited to the phase of the emitted SFG light. Locally chiral light overcomes this limitation by inducing interference between chiral SFG and achiral third harmonic generation, achieving ultimate enantio-sensitivity: one enantiomer remains dark, while the other emits a bright SFG signal.
2) We have introduced a concept of enantio-sensitive charge directed reactivity and conditions for its observation (Ordonez et al Communications Physics 2023). We uncovered the fundamental link between the direction of electron current and direction of motion of molecular fragments in chiral molecules and demonstrated that its enantio-sensitivity can reach 40 % -- extremely high value in comparison with sub-percent enantio-sensitivity of standard methods. These concepts contributed to the experimental (Callegari group, DESY) movies of ultrafast chiral currents excited in chiral molecules (Wanie et al, Nature 2024).
3) We have created a new type of structured light which is both locally chiral and has topological properties (Mayer et al, Nature Photonics 2024). Our set-up involves a combination of two-color tightly focused counter-rotating circularly polarised vortex beams such that light polarization vector draws a trefoil knot in time and forms a vortex with controlled topological charge in space. Our calculations show that such light enables robust detection of sub-percent values of enantiomeric excess. Topological robustness is due to conservation of topological charge –which remains unchanged under e.g. light intensity fluctuations. The major challenge was to extend our concepts to the situation when several topological charges co-exist. Such situation emerges due to the lack of control over circularity of incoming beams. Our work has been highlighted in the News and Views commentary (D. Smirnova et al Nature Photonics 2024).
4) Temporal geometry is recorded on sub-laser cycle time -scale. Is it possible to excite and detect temporal geometry in solids? Theoretically we have found a way to record and characterise the sub-cycle correlated charge dynamics in a model high temperature superconductor (Valmispild et al, Nature Photonics 2024) and also in a context of experiment (Biegert group, ICFO) on light driven topology in a two-dimensional material (Tulnev et al, Nature 2024). Thus the concepts of temporal geometry can be extended to correlated materials and chiral solids.
