Hexatic Phase in Covalent Two-Dimensional Silver Iodide

TL;DR

This study visualizes the hexatic phase in 2D silver iodide and provides evidence for a mixed melting scenario, contributing to the understanding of phase transitions in two-dimensional materials.

Contribution

It presents direct atomic-resolution imaging of the hexatic phase in 2D silver iodide, supporting a mixed melting scenario in line with theoretical predictions.

Findings

Observation of the hexatic phase in 2D silver iodide

Evidence for a mixed melting transition scenario

Use of advanced electron microscopy techniques

Abstract

According to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory, the transition from a solid to liquid in two dimensions proceeds through an orientationally ordered liquid-like hexatic phase. However, alternative mixed melting scenarios, in which melting proceeds through the hexatic phase with both continuous and discontinuous transitions, have also been observed in some two-dimensional systems. In this study, we imaged silver iodide embedded in multilayer graphene using time- and temperature-resolved in situ atomic-resolution scanning transmission electron microscopy and nanobeam electron diffraction. We observed the hexatic phase and provide evidence supporting a mixed melting scenario.