Ultrafast electronic and optical response of chiral molecules in gas phase provides opportunities for marrying chiral and topological properties with a benefit of generating new highly efficient and robust chiral observables not relying on interaction with magnetic field, in contrast to standard chiroptical methods. We present two vignettes to highlight emergent links between chirality and topology in (i) optical and (ii) electronic response.
(i) We introduce the concept of a chiral topological light, i.e. a vortex beam that is chiral at each point of the wavefront and is characterized by an azimuthally varying handedness described by an integer topological charge. We show the potential of this new type of light by using it to drive enantio-sensitive High-Harmonic Generation response in chiral molecules. The enantio-sensitivity arises as a spatial rotation of the far-field harmonic profile, which is robust against noise and allows us to easily infer enantiomeric excesses in mixtures of few percent.
(ii) We found geometric fields in photoionization of chiral molecules which depends on the photoelectron momentum k. When integrated over all directions of the photoelectron momentum, this field is equivalent to the Berry curvature. Crucially, it underlies new classes of enantio-sensitive observables. The first class involves scalar observables and is related to the photoionization and photo-excitation yield which turns out to be proportional to the Berry phase. The second class involves vectorial observables and is generated by the Berry curvature. The third class involves tensorial observables generated by the geometric field. All these observables are highly efficient because they do not rely on magnetic field, and appear already in the electric dipole approximation.