Pressure-Tunable Photonic Band Gaps in an Entropic Colloidal Crystal

TL;DR

This paper presents a pressure- and shape-tunable colloidal crystal that can reversibly switch between diamond and tetragonal diamond structures, enabling reconfigurable photonic properties inspired by atomic high-pressure transitions.

Contribution

It introduces a novel design of polyhedral particles capable of reversible structural transitions, inspired by atomic diamond transitions, for reconfigurable colloidal photonic materials.

Findings

Reversible pressure-induced transition between diamond and tetragonal diamond structures.

Shape change can trigger the structural transition in situ.

Potential for creating reconfigurable photonic band gap materials.

Abstract

Materials adopting the diamond structure possess useful properties in atomic and colloidal systems, and are a popular target for synthesis in colloids where a photonic band gap is possible. The desirable photonic properties of the diamond structure pose an interesting opportunity for reconfigurable matter: can we create a colloidal crystal able to switch reversibly to and from the diamond structure? Drawing inspiration from high-pressure transitions of diamond-forming atomic systems, we design a system of polyhedrally-shaped particles that transitions from diamond to a tetragonal diamond derivative upon a small pressure change. The transition can alternatively be triggered by changing the shape of the particle in-situ. We propose that the transition provides a reversible reconfiguration process for a potential new colloidal material, and draw parallels between this transition and phase behavior of the atomic transitions from which we take inspiration.