Speaker
Description
Twist-bend nematic $\left(N_\text{TB}\right)$ [1, 2] is a fifth member of the nematic family, beyond uniaxial $\left(N_\text{U}\right)$ and biaxial $\left(N_\text{B}\right)$ nematics, cholesteric $\left(N^{\ast}\right)$ and blue phases $\left(\text{BP}\right)$. Its uniqueness arises from a double degenerate ground-state (ambidextrous chirality) with a periodically modulated heliconical structure possessing a nanoscale pitch, which is formed from achiral bent-shaped molecules [3]. It is a profound example of so-called spontaneous (chiral) symmetry breaking in achiral materials. Despite the short time since the discovery, $N_\text{TB}$ has already found applications [4].
In this work [5], we present investigations based on Landau-de Gennes theory of chiral nematics, supplemented by terms representing molecular steric polarization [6]. With the helicity mode expansion for the alignment tensor $\mathbf{Q}(\mathbf{r})$ and the polarization $\mathbf{P}(\mathbf{r})$ fields we study relative stability and properties of $\left(N^{\ast}\right)$ and $\left(N_\text{TB}\right)$ for bent-core materials with chiral centers or dopants.
Acknowledgments
This work was supported by the Grant No. DEC-2013/11/B/ST3/04247 of the National Science Centre in Poland. W.T. acknowledges the financial support by Marian Smoluchowski Scholarship (KNOW/58/SS/WT/2016) from Marian Smoluchowski Cracow Scientific Consortium "Matter-Energy-Future" within the KNOW grant and by Jagiellonian Interdisciplinary PhD Programme co-financed from the European Union funds under the European Social Fund (POWR.03.05.00-00-Z309/17-00).
[1] I. Dozov, Europhys. Lett. 56, 247 (2001).
[2] V. Borshch et al., Nat. Commun. 4, 2635 (2013).
[3] R. Mandle, Soft Matter 12, 7883 (2016).
[4] J. Xiang et al., Adv. Mater. 27, 3014 (2015).
[5] L. Longa and W. Tomczyk, Liq. Cryst. 45, 2074 (2018).
[6] L. Longa and G. Pająk, Phys. Rev. E 93, 040701 (2016).
