This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A study has been published in Nature Communications that identifies an unusual regime of quantum oscillations in a three-dimensional topological insulator. The results show that, when subjected to temperatures near absolute zero and extreme magnetic fields, electrons in the material zirconium pentatelluride (ZrTe₅) exhibit behavior that deviates from the pattern predicted by conventional theory.
The study, led by researchers from the University of São Paulo (USP) in Brazil, Los Alamos National Laboratory and the University of Washington, among other U.S. institutions, combines electrical transport experiments conducted in magnetic fields of up to 60 tesla and at temperatures around 0.7 kelvin (-272.45 °C) with detailed theoretical modeling. "This work expands our understanding of electron transport in exotic phases of matter and suggests that topological insulators support the transport of not only electric charge, but also another fundamental degree of freedom: electron spin," says Julio Larrea Jiménez, a professor at USP's Physics Institute (IF) and co-founder and director of the Laboratory for Quantum Matter under Extreme Conditions (LQMEC). Larrea was the doctoral advisor for Cauê Kaufmann Ribeiro, the first author of the article.
Ribeiro conducted a significant portion of the experiments during an internship at the National High Magnetic Field Laboratory in Los Alamos. There, he was co-advised by Johanna Palmstrom and Sean Thomas. Topological insulators behave as insulators internally but conduct electricity on their surface.
This property stems from the topology of the electronic bands, or the global characteristics of the quantum structure of electronic states protected by crystal symmetries. ZrTe₅ is of particular interest because the material lies near the boundary between different topological phases. Minimal changes in temperature, mechanical deformation, composition or magnetic field can alter its electronic response.
For this reason, ZrTe₅ has become a prime platform for investigating topological phase transitions and relativistic quasiparticles in solids. Generally, when electrons move in a magnetic field, their orbits no longer have continuous energy. Quantum mechanics imposes discrete energy values, called Landau levels, named after the great Soviet physicist and mathematician Lev Landau (1908–1968).
In very pure metals, these levels successively cross the Fermi level—the energy separating occupied and empty electronic states—producing periodic oscillations in electrical resistance. These oscillations, known as Shubnikov–de Haas oscillations, exhibit regular periodicity in 1/B, where B is the magnetic field. However, something different occurred in the ZrTe₅ studied.
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