On the Microscopic Origin of Cholesteric Pitch
  We present a microscopic analysis of the instability of the nematic phase to chirality when molecular chirality is introduced perturbatively. We show that previously neglected short-range biaxial correlations play a crucial role in determining the cholesteric pitch. We propose an order parameter which quantifies the chirality of a molecule. 
A. B. Harris, Randall D. Kamien, T. C. Lubensky