"Ultra-weak" First-Order Phase Transition in Biaxial Liquid Crystals

Abstract

We report high-resolution Monte Carlo evidence characterizing the hierarchy of transition strengths in biaxial nematogens. By employing multiple histogram reweighting on large lattices, we demonstrate that while the isotropic-to-uniaxial ($I \to N_U$) transition is symmetry-enforced first-order, the uniaxial-to-biaxial ($N_U \to N_B$) transition in the region between the tricritical point and the triple point ($λ= 0.26$) is proximity-driven and more than an order of magnitude smaller for large system sizes. Such a class of ultra-weak first-order transitions could be a new pathway for future investigations.