Interfacially arrested melting in thin films: capillarity-driven suspension of phase transitions

TL;DR

This paper uncovers a regime where melting in molecularly thin films is halted by interfacial effects, allowing stable liquid droplets above the melting point and enabling sensitive thermal signal detection.

Contribution

It introduces the concept of interfacially arrested melting in thin films, demonstrating how capillary effects can suspend phase transitions independent of droplet size.

Findings

Stable liquid droplets exist above melting temperature.

Arrested melting depends on a single control parameter.

Thermal signals are intrinsically amplified by morphology changes.

Abstract

Melting is typically viewed as a bulk first-order phase transition that proceeds once nucleation barriers are overcome. Here we demonstrate an interfacially arrested melting regime in molecularly thin crystalline films, where large liquid droplets remain stably trapped well above the bulk melting temperature. Using long-chain alkane films as a model system, we show that melting is suspended by the competition between bulk melting enthalpy and interfacial energy costs associated with capillary confinement. The arrested state is governed by a single control parameter, the product of temperature offset and film thickness, and is independent of droplet size. As a consequence, small temperature variations produce pronounced and reversible changes in droplet morphology, enabling intrinsic thermodynamic amplification of thermal signals. These results reveal a general mechanism by which interfacial constraints can arrest first-order phase transitions in thin films.