Speaker
Description
Synopsis: We show how to imprint the handedness of locally chiral light into achiral matter, and how to monitor such achiral-to-chiral phase transitions in an all-optical setup. Our proof-of-principle simulations reveal that the hydrogen atom undergoes ultrafast and highly nonlinear chiral electron dynamics when exposed to an intense, ultrashort, locally chiral laser pulse, giving rise to chiral high harmonic generation. Whatsmore, the atom remains in a chiral superposition of stationary states after the pulse is gone, emitting chiral free-induction decay radiation which reveals the imprinted handedness.
Synthetic chiral light, introduced in [2], enables ultrafast and highly efficient imaging of molecular chirality. It is locally chiral: the tip of the electric-field vector draws a chiral (3D) Lissajous figure in time, at each point in space. Since its chirality is preserved within the electric dipole approximation, it achieves maximum chiral sensitivity. Interestingly, such tailored light can also be used to create chiral electronic states in atoms [3], which emit chiral photoelectron currents and exhibit photoelectron circular dichroism [3].
We demonstrate how synthetic chiral light, both locally and globally chiral [2], imprints and records chirality in achiral media. By driving ultrafast chiral electron motion in initially achiral systems, such as atoms, we induce ultrafast achiral-to-chiral phase transitions.
We solved the time-dependent Schrödinger equation for a hydrogen atom exposed to an ultrashort, intense, locally chiral field. The laser drives ultrafast chiral electron motion at its fundamental frequencies (800 nm and 400 nm) leading to the generation of high-frequency components creating a chiral structure in time. These components give rise to chiral high harmonic generation (HHG). After the pulse the atom remains in a chiral coherent superposition of stationary states, and thus the electron continues to undergo ultrafast time dependent chiral dynamics. Changing the relative phases of the components of the field varies the phase of our imprinted dynamics. We will introduce a novel chiral measure to describe the instantaneous chirality of the dipole motion. This measure accompanies the chiral correlation functions defined for our locally chiral field and describe the strength of the interaction between the field and chiral matter. This allows for robust characterization of our elliptically rotating time-dependent chirality.
We believe that this work creates exciting opportunities for driving and monitoring achiral-to-chiral phase transitions in all-optical setups, also in complex systems, as well as for driving chiral photo-chemical reactions using achiral reagents.
References
[1] Ordonez A F and Smirnova O 2019 Phys. Rev. A 99 043416
[2] Ayuso D et al 2019 Nat. Photon. 13 866
[3] Mayer N et al 2022 Phys. Rev. Lett. 129 243201
- E-mail: edward.binns19@imperial.ac.uk
