Material for future Quantum Computers

Jülich, 28. October 2021

Physicists at Forschungszentrum Jülich have succeeded in taking an important step towards the realization of novel electronic components. Using a special four-tip scanning tunneling microscope, they were able to measure, for the first time, the extraordinary electrical properties that exist in ultra-thin topological insulators. These result from the fact that the electron spin is coupled to the current direction, which is a prerequisite for use in a topological Quantum Computer.

Measurement with the 4-tip scanning tunneling microscope.
Forschungszentrum Jülich / Vasily Cherepanov

The high error-proneness of quantum bits, or qubits, is one of the main hurdles in building practical quantum computers. Topological Quantum Computers are considered an elegant and promising solution to this problem. The sensitive quantum information in such a computer is particularly well protected against errors due to the choice of certain materials. However, thus far, the concept only largely exists on paper. The search for a material system with the appropriate properties is still in full swing.

The idea of a topological Quantum Computer is based on the use of topological insulators. These are a novel class of materials with very special properties: The materials behave like an insulator in their interior, so they do not conduct electricity there, but their surface is conductive. The direction of motion is strictly coupled to the spin of the electrons.

Interesting for Quantum Computers and Spintronics

3D topological insulators, discovered only a few years ago, are a special case. When thinking of them as cubes, one can say that they are conductive on all six sides. However, researchers at Jülich's Peter Grünberg Institute for Quantum Nanoscience have now shown that the conductivity at the surface decreases as the 3D insulators are made thinner and thinner. What finally remains is a thin layer, only a few nanometers thick, with four conductive edges where electric current continues to flow in a directional manner.

Because of their special properties, the ultrathin topological insulators are interesting materials for applications in spintronics - that is, for the development of devices and components that use electron spin to process and store information. In combination with superconductors, they could also be suitable for realizing other, even more exotic effects that can be used in topological Quantum Computers.

Detection with "nano-multimeter"

For their measurements, the researchers used a special scanning tunneling microscope with four tips. The instrument, which was developed at Forschungszentrum Jülich, makes it possible to perform electrical measurements under high-purity conditions on extremely small structures. The current study also used a new method that makes the positioning of the measuring tips even more precise with an accuracy of a few nanometers.

Using the "nano-multimeter," the researchers were able to demonstrate for the first time that the nanoscale electrical properties of the thin films behave as theoretically predicted. The observation is important for a deeper understanding of the topological insulators and crucial for their further development with a view to potential applications.

Original publication:

Lifting the Spin-Momentum Locking in Ultra-Thin Topological Insulator Films

Arthur Leis, Michael Schleenvoigt, Vasily Cherepanov, Felix Lüpke, Peter Schüffelgen, Gregor Mussler, Detlev Grützmacher, Bert Voigtländer,* and F. Stefan Tautz

Advanced Quantum Technologies (published online 9 September 2021), DOI: 10.1002/qute.202100083

Further information:

Peter Grünberg Institute, Quantum Nanoscience (PGI-3)

Research Group "Multitip scanning probe microscopy"


Dr. Felix Lüpke
Peter Grünberg Institute, Quantum Nanoscience (PGI-3)
Tel.: +49 2461/61-4553

Prof. Bert Voigtländer
Head of the research group "Multitip scanning probe microscopy" at the Peter Grünberg Institute, Quantum Nanoscience (PGI-3)
Tel.: +49 2461 61-4116

Prof. Dr. F. Stefan Tautz
Head of the Peter Grünberg Institute, Quantum Nanoscience (PGI-3)
Tel: + 49 2461 61-4561

Press contact:

Tobias Schlößer
Corporate Communications
Forschungszentrum Jülich
Tel.: +49 2461 61-4771

Last Modified: 16.08.2022