As the gold tip of the atomic force microscope is moved across the surface of the topological insulator, it experiences energy loss only at discrete, quantized energies. This is related to the image potential states that are formed over the conducting surface of the topological insulator. Image: University of Basel, Department of Physics.
As the gold tip of the atomic force microscope is moved across the surface of the topological insulator, it experiences energy loss only at discrete, quantized energies. This is related to the image potential states that are formed over the conducting surface of the topological insulator. Image: University of Basel, Department of Physics.

Topological insulators are innovative materials that conduct electricity on the surface, but act as insulators on the inside. Researchers from Switzerland and Turkey have begun investigating how these materials react to friction, and have discovered that the heat generated by friction is significantly lower than in conventional materials. This is due to a new quantum mechanism, which the researchers report in a paper in Nature Materials.

Thanks to their unique electrical properties, topological insulators promise many innovations in the electronics and computer industries, as well as in the development of quantum computers. Their thin surface layer can conduct electricity almost without resistance, meaning they generate less heat than traditional materials. This makes them of particular interest for electronic components.

Furthermore, the electronic friction – i.e. the electron-mediated conversion of electrical energy into heat – in topological insulators can be reduced and controlled. Researchers at the University of Basel in Switzerland and the Istanbul Technical University in Turkey have now been able to experimentally verify and demonstrate exactly how the transition from energy to heat through friction behaves – a process known as dissipation.

The team, headed by Ernst Meyer in the Department of Physics at the University of Basel, investigated the effects of friction on the surface of the topological insulator bismuth telluride. To do this, the scientists used an atomic force microscope in pendulum mode, in which a conductive microscope tip made of gold oscillates back and forth just above the two-dimensional surface of the topological insulator. When a voltage is applied to the microscope tip, the movement of the pendulum induces a small electrical current on the surface.

In conventional materials, some of this electrical energy is converted into heat through friction. But on the conductive surface of the topological insulator, the researchers found that the loss of energy through the conversion to heat was significantly reduced.

"Our measurements clearly show that at certain voltages there is virtually no heat generation caused by electronic friction," explains Dilek Yildiz, who is also in the Department of Physics at the University of Basel.

The researchers were able to observe for the first time a new quantum-mechanical dissipation mechanism that occurs only at certain voltages. Under these conditions, the electrons migrate from the tip through an intermediate state into the material – similar to the tunneling effect in scanning tunneling microscopes. By regulating the voltage, the scientists were able to influence this dissipation.

"These measurements confirm the great potential of topological insulators, since electronic friction can be controlled in a targeted manner," says Meyer.

This story is adapted from material from the University of Basel, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.