constituents. The most celebrated may be quantum Hall systems, occurring at high magnetic fields in 2D electron gas materials such as GaAs heterostructures. Electrons combined with magnetic flux vortices carry current. Graphene exhibits charge fractionalization. Attempts have been made to extend fractional behavior to 3D systems. Surface states in topological insulators of various compounds (e.g. tellurium alloys, antimony), and pure metal (bismuth) crystals have been explored for fractionalization signatures. Notes Theoretical physics Quasiparticles