G. Poy – 20 novembre

In the past 10 years, major developments in the field of soft matter have unlocked the possibility of creating and controlling complex birefringent structures such as Hopf fibrations, knots/links, cholesteric fingers and torons. These structures can be stabilized in anisotropic soft materials — such as liquid-crystal based mixtures — when chiral molecules are added to the system: here, the main role of chirality is to induce meta-stability in the free energy landscape of the sample, thus opening the way to a lot of exciting and novel structures of interest for topological soft matter and optical applications.

In this seminar, I will talk about other, perhaps less known, aspects of chirality in soft matter. I will first present some of the results obtained during my PhD concerning the Lehmann effect, an out-of-equilibrium effect which couples a temperature gradient with the rotation of the internal texture of liquid crystal droplets in coexistence with the isotropic phase. I will explore the role of chirality at the microscopic/macroscopic level in this system, and review some of the theoretical models proposed to explain the Lehmann effect. I will then move to more recent research done during my postdoc on optics in anisotropic soft materials. After a short outlook on the numerical tools that I developed for light propagation in arbitrary birefringent materials, I will show how chirality can be leveraged to enhance the effective Kerr response in spatial light solitons, and how the same solitons can potentially interact with the birefringent structures mentioned at the beginning of this abstract.