"Construction manual" for quantum materials

Overview

Physicists from the Würzburg–Dresden Cluster of Excellence ct.qmat – Complexity and Topology in Quantum Matter have discovered a minimum distance at which electrons in wires made of quantum materials must flow in order to conduct electricity in a dissipationless manner. Due to these findings, the use of so-called topological insulators in electronic components nears a step closer. Since the first demonstration of this new class of materials in 2007 by a member of the cluster, worldwide research into topological quantum materials has been booming. After all, they promise "green electronics" that will make future technologies more sustainable. The current research results have been published in the journal Physical Review Letters.

Topological insulators – hope for eco-friendly technology
In electronic devices, the individual components are connected by myriads of wires which route signals from one place to another. The stream of electrons in wires made from topological materials flows almost dissipation-less, thereby reducing losses and unintended heating effects to a minimum and offering advantages over conventional wires, made, e.g., from copper. Thus, the still young material class of topological insulators promises less waste heat and lower energy consumption and, thereby, a greener information technology. Since their first demonstration at Julius-Maximilians-University Würzburg (JMU) in 2007, these materials of the future have been intensively researched there and since 2019 in the Würzburg-Dresden Cluster of Excellence ct.qmat.  

The distance is what matters
However, the density at which topological wires can be packed was not known so far. A research team from Chair for Experimental Physics II at JMU have systematically explored how adjacent wires of lead-tin-selenide (PbSnSe) – a topological insulator – interact.
 
"This allows us for the first time to precisely define the minimum distance between electron orbits on the material surface of topological insulators and to understand topological quantum material a little better once again," comments Prof. Matthias Bode, project leader and founding member of the Cluster of Excellence ct.qmat.
 
The current research results reveal that topological wires made of the studied quantum material PbSnSe conduct electricity without loss only with a minimum spacing of 25 nanometers (nm). At shorter distances, the topologically protected state becomes more and more distorted. At wire distances below 10 nm, the topological character of the wires is completely lost.

Outlook
Currently, the researchers are studying the influence of magnetic atoms on the transport properties of topological electron wires.

Participants
In addition to cluster members from the Julius Maximilians University of Würzburg, scientists from the Polish Academy of Sciences, from which the material samples were obtained, were also involved in the publication. The experiments were carried out by the Würzburg physicists Johannes Jung and Dr. Artem Odobesko.