# Groupe de Physique Statistique

## Equipe 106, Institut Jean Lamour

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### Articles dans des revues à comité de lecture

 Tetrahedratic mesophases, chiral order, and helical domains induced by quadrupolar and octupolar interactions Trojanowski K., Pajak G., Longa L., Wydro T. Phys. Rev. E 86 (2012) 011704 DOI : 10.1103/PHYSREVE.86.011704 We present an exhaustive account of phases and phase transitions that can be stabilized in the recently introduced generalized Lebwohl-Lasher model with quadrupolar and octupolar microscopic interactions [L. Longa, G. Pająk, and T. Wydro, Phys. Rev. E 79, 040701(R) (2009)]. A complete mean-field analysis of the model, along with Monte Carlo simulations allows us to identify four distinct classes of the phase diagrams with a number of multicritical points where, in addition to the standard uniaxial and biaxial nematic phases, the other nematic like phases are stabilized. These involve, among the others, tetrahedratic ($T$), nematic tetrahedratic ($NT$), and chiral nematic tetrahedratic ($N^∗_T$) phases of global $T_d$, $D_{2d}$, and $D_2$ symmetry, respectively. Molecular order parameters and correlation functions in these phases are determined. We conclude with generalizations of the model that give a simple molecular interpretation of macroscopic regions with opposite optical activity (ambidextrous chirality), observed, e.g., in bent-core systems. An estimate of the helical pitch in the $N^∗_T$ phase is also given.