New Insights into the Interaction of Topological Insulators

Jülich, 24 August 2022 – Tungsten di-telluride (WTe₂) has recently proven to be a promising material for the realization of topological states. These are regarded as the key to novel "spintronic" devices and quantum computers of the future due to their unique electronic properties. Physicists at Forschungszentrum Jülich have now been able to understand for the first time how the topological properties of multilayer WTe­₂ systems can be changed systematically by means of studies under a scanning tunneling microscope. The results have been published in the journal Nano Letters.

Topological insulators became known beyond expert circles thanks to the 2016 Nobel Prize in Physics. However, their research is still quite in its beginnings, and many fundamental questions remain unanswered. One of the distinguishing features of the compound WTe₂ is that it exhibits a whole range of exotic physical phenomena depending on its layer thickness. Atomically thin layers are insulating on the surface, but due to their crystal structure they exhibit so-called topologically protected edge channels. These edge channels are electrically conductive and the conduction depends on the spin of the electrons. If two such layers are stacked on top of each other, crucially different interactions occur depending on how the layers are aligned.

If the two layers are not aligned, the conductive edge channels in the two layers interact only minimally. However, if they are twisted by exactly 180°, the topological protection as well as the edge channels disappear and the entire system becomes insulating. Furthermore, with a minimal twist of only a few degrees, a periodic superstructure, a so-called moiré lattice, forms, which additionally modulates the electrical conductivity. Researchers at the Peter Grünberg Institute (PGI-3) have now been able to study these properties locally on the atomic scale for the first time using a scanning tunneling microscope giving crucial insights into the interactions between the layers.

Original publication:

Quantum Spin Hall Edge States and Interlayer Coupling in Twisted Bilayer WTe₂
Felix Lüpke, Dacen Waters, Anh D. Pham, Jiaqiang Yan, David G. Mandrus, Panchapakesan Ganesh, and Benjamin M. Hunt
Nano Lett. (27 June 2022), DOI: 10.1021/acs.nanolett.2c00432

Contacts

Dr. Felix Lüpke

• Peter Grünberg Institute (PGI)
• Quantum Nanoscience (PGI-3)

Building 02.4w /
Room 301

+49 2461/61-6977

E-Mail

Tobias Schlößer

Pressereferent

Building 15.3 /
Room R 3028a

+49 2461/61-4771

E-Mail

Further information

Quantum Computing

Jülich Quantum Researchers Build First Hybrid Quantum Bit Based on Topological Insulators

With their superior properties, topological qubits could help achieve a breakthrough in the development of a quantum computer designed for universal applications. So far, no one has yet succeeded in unambiguously demonstrating a quantum bit, or qubit for short, of this kind in a lab. However, scientists from Forschungszentrum Jülich have now gone some way to making this a reality.

Institute

Quantum Nanoscience (PGI-3)

Fundamental research in quantum nanoscience is of utmost importance for the emerging quantum technologies, including quantum computing. We use our extensive knowledge in surface science and nanoscience to contribute to quantum nanoscience and its primary goal: the manipulation and exploitation of quantum-coherent functionality in nanostructures.

Research group

Layered quantum systems

Van der Waals heterostructures enable the engineering of exotic quantum states by proximity effects. We use cutting-edge techniques for the fabrication of ultraclean heterostructures - a crucial requirement to study their properties with our state-of-the-art scanning probe microscopes.