Two-dimensional melting under quenched disorder

TL;DR

This study investigates how quenched disorder affects two-dimensional melting, confirming the Kosterlitz-Thouless-Halperin-Nelson-Young scenario and revealing that disorder broadens the hexatic phase's stability range.

Contribution

It provides experimental and simulation evidence on the impact of quenched disorder on 2D melting, especially on phase transition shifts and fluctuations.

Findings

Hexatic phase stability is increased by disorder.

Fluid-hexatic transition remains unaffected.

Hexatic-solid transition shifts to lower temperatures.

Abstract

We study the influence of quenched disorder on the two-dimensional melting behavior by using both video-microscopy of superparamagnetic colloidal particles and computer simulations of repulsive parallel dipoles. Quenched disorder is provided by pinning a fraction of the particles. We confirm the occurrence of the Kosterlitz-Thouless-Halperin-Nelson-Young scenario with an intermediate hexatic phase. While the fluid-hexatic transition remains largely unaffected by disorder, the hexatic-solid transition shifts towards lower temperatures for increasing disorder resulting in a significantly broadened stability range of the hexatic phase. In addition, we observe spatio-temporal critical(-like) fluctuations consistent with the continuous character of the phase transitions.