Direct observation of colloidal quasicrystallization

Abstract

Discovered first in synthetic alloys and subsequently in nature, quasicrystals exhibit forbidden symmetries and long-range orientational order but lack translational periodicity. Despite numerous theoretical and numerical studies, the fabrication of quasicrystals remains a challenge, with limited means available for observing their formation in situ. As a result, questions remain regarding the detailed mechanisms of quasicrystal formation and stabilization. Observable under optical microscopes, micrometre-scale colloidal systems have been used for decades as atomic models with considerably slowed-down dynamics and tuneable interactions through surface modification, solution composition and applied external fields. Here we show that two-dimensional dodecagonal quasicrystals can be reversibly assembled from single-component microspheres using a combination of orthogonally applied magnetic and electric fields. Varying the magnitude and frequency of the applied fields not only determines the resulting structures but also sets the phase transition dynamics via an effective system temperature. We hypothesize that these quasicrystals are energetically stabilized with their formation driven by an isotropic double-well pair potential, although the origin of the second minimum remains an open question.