17-Sep-2018 - Universidad del País Vasco / Euskal Herriko Unibertsitatea

Bismuth shows novel conducting properties

Topological insulators are materials that insulate on the inside but conduct electrical current on their surface. The current flow without resistance and respond in unconventional ways to electric and magnetic fields. These unique properties are studied with real interest towards future applications in high-performance electronics and quantum computation.

Recently, a new class of topological materials with novel conducting properties on the edges of crystals rather than on their surface was predicted by a group of physicists from Donostia International Physics Center (DIPC), the University of the Basque Country (UPV/EHU), UZH, Princeton University and Max Planck Institute of Microstructure Physics. The new material was given the name of "higher-order topological insulator".

According to theoretical studies, the conducting edges are extraordinarily robust for higher-order topological insulators: the current of topological electrons cannot be stopped by impurities and if the crystal breaks, the new edges automatically also conduct current. However, the most extraordinary property of these new materials is that they can in theory conduct electricity without any dissipation as superconductors do at low temperatures. This would be a specific property of higher-order class topological insulators.

Bismuth is topological

Now, thanks to a wider scientific collaboration where scientists from Paris-Sud University and CNRS were also involved, it has been confirmed that bismuth, an element consistently described as bulk topologically trivial, follows a generalized bulk-boundary correspondence of higher-order, that is, hinges host topologically protected conducting modes instead of the surface of the crystal.

The special topological properties of this element were first identified by using symmetry arguments, topological indices, first-principles calculations, and the recently introduced framework of topological quantum chemistry.

This phenomenon was then verified experimentally. With scanning-tunneling spectroscopy, the unique signatures of the rotational symmetry of the one-dimensional states located at step edges of the crystal surface were proved. Using Josephson interferometry, scientists demonstrated their universal topological contribution to the electronic transport.

Finally, this work establishes bismuth as a higher-order topological insulator and opens the way to identify new ones.

  • Frank Schindler, Zhijun Wang, Maia G. Vergniory, Ashley M. Cook, Anil Murani, Shamashis Sengupta, Alik Yu. Kasumov, Richard Deblock, Sangjun Jeon, Ilya Drozdov, Hélène Bouchiat, Sophie Guéron, Ali Yazdani, B. Andrei Bernevig & Titus Neupert; "Higher-order topology in bismuth"; Nature Physics volume 14, pages 918-924 (2018).
Facts, background information, dossiers
  • topological insulators
  • Euskal Herriko Unib…
  • higher-order topolo…
More about UPV/EHU
  • News

    The first nanometrically-sized superelastic alloy

    UPV/EHU-University of the Basque Country's researchers have explored superelasticity properties on a nanometric scale based on shearing an alloy's pillars down to nanometric size. The researchers have found that below one micron in diameter the material behaves differently and requires much ... more

    Using a simple, scalable method, a material that can be used as a sensor is developed

    Erlantz Lizundia, a researcher in the UPV/EHU's department of Physical Chemistry and expert in cellulose, started the research during a period of time he spent in Canada. The research group he was in specialised in the helix-shaped organisation of a product extracted from cellulose, cellulo ... more

    Studying fundamental particles in materials

    Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity to observe particle properties that have no realization in elementary particles. In the present study, an international research tea ... more