Violation of Ericksen inequalities in lyotropic chromonic liquid crystals

TL;DR

This paper explores the elastic properties of lyotropic chromonic liquid crystals, revealing a unique intermediate regime where Ericksen inequalities are violated yet the system remains stable, impacting their structural behavior.

Contribution

It identifies and analyzes an intermediate elastic regime in lyotropic chromonic liquid crystals where Ericksen inequalities are violated without compromising stability.

Findings

Lyotropic chromonic liquid crystals are in an intermediate elastic regime.

The director field structure depends on system geometry.

Violations of Ericksen inequalities do not necessarily lead to instability.

Abstract

By analyzing elastic theory for nematic liquid crystals, we distinguish three regimes of elastic constants. In one regime, the Ericksen inequalities are satisfied, and the ground state of the director field is uniform. In a second regime, certain necessary inequalities are violated, and the free energy is thermodynamically unstable. Between those possibilities, there is an intermediate regime, where the Ericksen inequalities are violated but the system is still stable. Remarkably, lyotropic chromonic liquid crystals are in the intermediate regime. We investigate the nonuniform structure of the director field in that regime, show that it depends sensitively on system geometry, and discuss the implications for lyotropic chromonic liquid crystals.