Skyrmions in Blue Phases of Chiral Liquid Crystals
a Condensed Matter Physics Department, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
b Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
Abstract.–Skyrmions are topologically protected, vortex-like formations of a field that cannot be removed by any smooth transformation and emerge in a range of fundamentally different, either quantum or classical systems, from spin textures, to chiral ferromagnets and chiral complex fluids. We show experimentally and numerically that the Blue Phase III of a chiral liquid crystal is a 3D fluid of chiral skyrmion filaments of the nematic orientational field, entangled with a 3D network of topological defect lines. It is an effective 3D dynamic fluid determined by the thermal fluctuations of two distinct branches of excitations: rapid internal fluctuations of the skyrmion structure and a slow collective motion of the skyrmion filaments. When confined to less than 150 nm layer, the 3D bulk skyrmion fluid transforms into a different effectively 2D liquid of half-skyrmions, with the dynamics of the skyrmion liquid slowing down by an order of magnitude, and with the individual skyrmions lingering, and even disappearing into, and reappearing from the homogeneous liquid crystal. The BPIII and BPI phases are therefore made of skyrmions, which when confined to less than 150 nm cells, transform equally into a 2D half-skyrmion liquid. The temperature range of this 2D half-skyrmion liquid is much broader than the temperature interval of BP phases, which makes BP materials interesting for broad temperature range skyrmionic applications.