When graphene nanoribbons contain sections of varying width, very robust new quantum states can be created in the transition zone.
Empa researchers, together with researchers from the Max Planck Institute for Polymer Research in Mainz and other partners, have achieved a breakthrough that could in future be used for precise nanotransistors or - in the distant future - possibly even quantum computers, as the team reports in the current issue of the scientific journal «Nature». A material that consists of atoms of a single element, but has completely different properties depending on the atomic arrangement - this may sound strange, but is actually reality with graphene nanoribbons. The ribbons, which are only a few carbon atoms wide and exactly one atom thick, have very different electronic properties depending on their shape and width: conductor, semiconductor or insulator. An international research team led by Empa's «nanotech@surfaces» laboratory has now succeeded in precisely adjusting the properties of the ribbons by specifically varying their shape. The particular feature of this technology is that not only can the «usual» electronic properties mentioned above be varied - it can also be used to generate specific local quantum states. So what's behind it? If the width of a narrow graphene nanoribbon changes, in this case from seven to nine atoms, a special zone is created at the transition: because the electronic properties of the two areas differ in a special, so-called topological way, a «protected» and thus very robust new quantum state is created in the transition zone. This local electronic quantum state can now be used as a basic component to produce tailor-made semiconductors, metals or insulators - and possibly even as a component in quantum computers.
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