A study published in Nature Communications has revealed an unusual form of quantum oscillation in a three-dimensional topological insulator. The findings show that electrons in zirconium pentatelluride (ZrTe5) can behave in unexpected ways when exposed to temperatures close to absolute zero and extremely powerful magnetic fields. The research was led by scientists from the University of São Paulo (USP) in Brazil, Los Alamos National Laboratory, the University of Washington, and other U.S. institutions.
The team combined electrical transport experiments performed in magnetic fields as strong as 60 tesla and at temperatures near 0.7 kelvin (-272.45 °C) with detailed theoretical calculations. "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 served as the doctoral advisor of Cauê Kaufmann Ribeiro, the study's first author.
Ribeiro carried out a large portion of the experimental work during an internship at the National High Magnetic Field Laboratory in Los Alamos, United States, supported by a FAPESP Research Internship Abroad. While there, he was co-advised by Johanna Palmstrom and Sean Thomas. A Material With Two Electronic Personalities Topological insulators have an unusual combination of properties.
Their interiors behave as electrical insulators, while their surfaces can conduct electricity. This behavior arises from the topology of their electronic bands, which describes broad features of the quantum structure of electronic states that are protected by crystal symmetries. ZrTe5 is especially valuable for studying this type of physics because it sits close to the boundary separating different topological phases.
Small changes in temperature, mechanical deformation, chemical composition, or magnetic field can significantly alter its electronic behavior. That sensitivity has made ZrTe5 an important material for investigating topological phase transitions and relativistic quasiparticles in solids. When electrons move through a magnetic field, their possible energies no longer form a continuous range.
Quantum mechanics restricts them to specific energy values known as Landau levels, named after the Soviet physicist and mathematician Lev Landau (1908-1968). In very pure metals, these Landau levels can repeatedly pass through the Fermi level, the energy boundary between occupied and unoccupied electronic states. Each crossing can produce an oscillation in electrical resistance.
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