Photo-induced chirality in a non-chiral material

Chirality is a form of symmetry closely related to the physical properties of solids and the chemical and biological activity of molecular systems. However, inducing chirality in a non-chiral material is challenging, because it requires breaking all mirrors and all roto-inversions simultaneously.

In this talk, I will show how nonlinear phononics, a protocol for rationally designing the structure and symmetry of crystals with light,^1,2 can be used to induce chirality of either handedness in the non-chiral piezoelectric material BPO₄.

At equilibrium, two compensated sub-structures of opposite handedness coexist within the unit cell of this material. By resonantly driving either one of two orthogonal, doubly degenerate infrared-active phonon modes with intense mid-infrared light pulses, we were able to displace a second lattice distortion with a positive or negative amplitude, uncompensating the staggered chirality and creating a picosecond-lived structure with either handedness. The optical activity of the transient chiral phases is comparable to the static value of prototypical chiral α-quartz, limited by the strength of the strength of the mid-infrared excitation pulse used in our experiment.

These findings offer new prospects for the control of out-of-equilibrium quantum phenomena in complex materials.