The topological matters are formed by template growth of filamentary substance, such as NbSe3 "whisker" crystal. The formation takes place during a direct vapor-phase reaction of niobium and selenium. Throughout a reaction process, residual gas/liquid selenium, one of the ingredients, is believed to assist crystallization by advecting NbSe3 molecules to their growing points. We found that the reactant, thin NbSe3 whiskers, can be attached to small droplets of selenium in the atmosphere by the force of surface tension. As a result, whiskers are spooled by droplets, forming a loop encircling the droplets.
Three classes of closed loop-shaped crystals are obtained by now. They are characterized by twists (no twist, pai and 2pai twist) introduced during their spooling process. The below figure describes how the three types of matters are formed.
Currently no other artificial way, like grinding, mechanical transformation or CVD technique, are able to produce single crystals with such topologies.