Using a special four-tip scanning tunneling microscope at Forschungszentrum Jülich, the extraordinary electrical properties that exist in ultra-thin topological insulators have been measured for the first time. These result from the fact that the electron spin is coupled to the direction of the current, which is a prerequisite for use in a topological quantum computer.
The use of topological insulators could minimize the current susceptibility of quantum bits to errors. The search for a material system with suitable properties is still in full swing.
Topological insulators behave like an insulator on the inside, i.e. they do not conduct electricity there, but their surface is conductive. The direction of movement is strictly coupled to the spin of the electrons. 3D topological insulators, which were only discovered a few years ago, are a special case. If you imagine them as a cube, they are conductive on all six sides. However, the conductivity at the surface decreases when they are made thinner and thinner, as researchers at Jülich's Peter Grünberg Institute of Quantum Nanoscience have now been able to show. What ultimately remains is a thin layer, only a few nanometers thick, with four conductive edges along which electric current continues to flow in a directional manner.
The current study also used a new method that makes the positioning of the measuring tips even more precise, with an accuracy of just a few nanometers.
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