Research led by the Universities of St Andrews and Tokyo reveals a new understanding on how to create topological electronic states in solids which could fuel the development of improved materials for fast and energy-efficient electronic devices. The findings could lead to new types of computer chips that could be much more powerful than those found in today's computers and smart phones.
The way in which electrons behave inside a solid is governed by its electronic structure, an intertwined network of 'bands' which define the allowed energies and momenta of electrons in the solid. If the right type ofbandscross over, this can give rise to interesting, and potentially extremely useful, physical properties of materials. For example, it was recently realised that isolated touching points of these bands can be stabilised by certain crystalline symmetries, creating so-called Dirac fermions in the bulk electronic structure. This allows electrons in the bulk of the crystal to behave as though they were massless particles, effectively a bulk analogue of the atomically-thin material graphene. As well as being an exciting playground for studying fundamental concepts of particles in physics, this can lead to ultra-high mobility of charge carriers, a property that could be used to make extremely good conductors.