Researchers at the University of Michigan have made a groundbreaking discovery in materials science, revealing unexpected quantum oscillations within an insulating material. This finding challenges long-standing assumptions about how materials conduct electricity and offers a new perspective on the dual nature of certain compounds, suggesting they can behave both as metals and insulators.
The research, conducted at the National Magnetic Field Laboratory, indicates that the quantum oscillations originate from the bulk of the material rather than its surface, a revelation that could reshape scientific understanding in the field. The study, published in Physical Review Letters, was supported by the U.S. National Science Foundation and the U.S. Department of Energy.
Understanding Quantum Oscillations
Quantum oscillations are a phenomenon where electrons behave in a manner akin to tiny springs, responding dynamically to magnetic fields. In metals, these oscillations are well-documented, allowing scientists to manipulate electron behavior by varying magnetic field strength. However, the recent discovery of similar oscillations in insulators—materials typically known for their inability to conduct electricity—has led to significant debate about whether these effects arise solely from surface interactions or deep within the material’s structure.
The research team, led by physicist Lu Li, collaborated with international scientists to investigate this mystery. Their findings confirm that the oscillations are indeed a bulk effect, suggesting a more complex underlying mechanism than previously understood. “What we have right now is experimental evidence of a remarkable phenomenon,” Li stated. “We’ve recorded it, and hopefully, at some point, we’ll realize how to use it.”
A New Duality in Materials Science
Li describes this discovery as indicative of a “new duality” in materials, reminiscent of the earlier realization that light and matter can display both wave and particle properties. The original duality has led to technological advancements such as solar cells and electron microscopes. The emerging duality suggests that certain insulating materials, like the compound ytterbium boride (YbB12), can exhibit both conductive and insulating properties, particularly under extreme magnetic conditions.
The research utilized a magnetic field of up to 35 Tesla, significantly stronger than the fields found in standard hospital MRI machines. “We’re showing that the naive picture of a surface with good conduction is completely wrong,” Li explained. “It’s the whole compound that behaves like a metal even though it’s an insulator.”
The team, which included more than a dozen scientists from six institutions, also featured notable contributions from researchers such as Kuan-Wen Chen and graduate students from the University of Michigan. Chen expressed enthusiasm about the clarity provided by their results, stating, “We are excited to provide clear evidence that it is bulk and intrinsic.”
This research not only unravels a fundamental question regarding the nature of carrier origins in insulators but also raises new inquiries about the behavior of materials at the quantum level. “We don’t yet know what kind of neutral particles are responsible for the observation,” remarked graduate student Yuan Zhu. “We hope our findings motivate further experiments and theoretical work.”
The project received additional funding and support from organizations such as the Institute for Complex Adaptive Matter, the Gordon and Betty Moore Foundation, and the Japan Society for the Promotion of Science. As scientists continue to explore these puzzling behaviors, this discovery marks a significant step forward in understanding the complexities of quantum materials.
