Evidence for critical-like behavior in ultraslowing glass-forming systems

Abstract

Glass transition constitutes one of main problems of condensed matter physics and material engineering that remains unsolved. The common acceptance of the Vogel-Fulcher-Tammann (VFT) equation for portraying the primary relaxation time or shear viscosity indicated a possible phase transition, hidden below the glass transition temperature (T(g)). Recently Hecksher [Nat. Phys. 4, 737 (2008)] delivered strong empirical arguments that VFT description lacks a direct experimental basis and thus theories not predicting a dynamic divergence should be focused on. We present clear evidence for a superiority of critical-like divergent equation τ(T)=τ(0)(T-T(C))(-ϕ) and T(C)<T(g) for liquid crystalline (LC) glass formers and orientationally disordered crystals (ODIC). Such dependence was already known for spin-glasslike systems and the dynamical scaling model, although the latter was hardly explored so far. The pressure-related behavior is also discussed. Results obtained support arguments for the suggested direct link between critical phenomena and vitrification [Tanaka, Nat. Mater. 9, 324 (2010)]. LCs and ODICs may be considered as simple experimental model systems for the structural glass formers group.