Soft-Pinning: Experimental Validation of Static Correlations in Supercooled Molecular Glass-forming Liquids

Enormous enhancement in the viscosity of a liquid near its glass transition is generally connected to the growing many-body static correlations near the transition, often coined as `amorphous ordering'. Estimating the length scales of such correlations in different glass-forming liquids is highly important to unravel the physics of glass formation. Experiments on molecular glass-forming liquids become pivotal in this scenario as the viscosity grows several folds ($\sim 10^{14}$), simulations or colloidal glass experiments fail to access the long-time scales required. Here we design an experiment to extract the static length scales in molecular liquids using dilute amounts of another large molecule as a pinning site. Results from dielectric relaxation experiments on supercooled glycerol with different pinning concentrations of sorbitol and the simulations on a few model glass-forming liquids with pinning sites indicate the robustness of the proposed method, opening a plethora of opportunity to study the physics of other glass-forming liquids.