A research team led by Professor Lu Li at the University of Michigan, along with an international group of collaborators, has observed quantum oscillations in a material that should not conduct electricity, challenging long-standing assumptions about how matter behaves. Their findings, provide evidence that the phenomenon originates in the bulk of the material, not just at its surface, opening questions about a possible “new duality” between insulators and conductors.
Chen, K.-W., Zhu, Y., Ratkovski, D., Zheng, G., Zhang, D., Chan, A., Jenkins, K., Blawat, J., Asaba, T., Iga, F., Varma, C. M., Matsuda, Y., Singleton, J., Bangura, A. F., & Li, L. (2025). Quantum Oscillations in the Heat Capacity of Kondo Insulator <math display="inline"> <mrow> <msub> <mrow> <mi>YbB</mi> </mrow> <mrow> <mn>12</mn> </mrow> </msub> </mrow> </math>. Physical Review Letters, 135(15), 156501. https://doi.org/10.1103/ms3x-pjsk
Quantum oscillations are typically observed in metals, where electrons respond to magnetic fields like tiny springs, producing measurable oscillations. In recent years, similar oscillations have been detected in insulators; materials that normally do not conduct heat or electricity; raising fundamental questions about their origin. Are these oscillations merely a surface effect, or do they emerge from the bulk of the material itself?
To answer this, Li and his team performed experiments at the National Magnetic Field Laboratory, the world’s largest and most powerful facility of its kind. Their results demonstrate that the oscillations are bulk and intrinsic, rather than a surface phenomenon.
Professor Lu Li at the University of Michigan stated,
“Effectively, we’re showing that this naive picture where we envisioned a surface with good conduction that’s feasible to use in electronics is completely wrong. It’s the whole compound that behaves like a metal even though it’s an insulator. Unfortunately, this crazy metal behavior only occurs at 35 Tesla; a magnetic field strength that’s about 35 times what’s inside an MRI machine.”
“Confirming that the oscillations are bulk and intrinsic is exciting,” says Yuan Zhu, a graduate student involved in the study. “We don’t yet know what kind of neutral particles are responsible for the observation, but it motivates further experiments and theoretical exploration.
Li describes this phenomenon as a possible new duality. Historically, duality in quantum mechanics referred to the particle-wave duality of light and matter. In this context, the duality refers to a material that behaves simultaneously as a conductor and an insulator, a behavior that contradicts conventional understanding.
The material studied, ytterbium boride (YbB12), exhibits this unusual conduction behavior under extremely strong magnetic fields, around 35 Tesla—about 35 times stronger than the magnetic field used in typical MRI machines. Despite the extreme conditions, the findings raise fundamental questions about how materials can conduct in ways previously thought impossible.
Professor Li notes, “Effectively, the whole compound behaves like a metal even though it is an insulator. While immediate applications may be limited due to the extreme magnetic field required, this discovery challenges how we classify materials and encourages further investigation into exotic quantum phenomena.”
While practical applications are not yet clear, the discovery highlights how quantum materials can defy standard classification, potentially informing future studies in electronics, optics, and quantum devices. Understanding how these oscillations occur could provide insights for developing new materials that exploit similar quantum behaviors under more accessible conditions.
“This work provides a platform for asking deeper questions about neutral particle behavior and conduction in insulators,” says Kuan-Wen Chen, research fellow on the project. “Our findings give experimental evidence that can guide both theory and future exploration.”
The team hopes that these results will motivate additional research in quantum materials, further bridging the gap between fundamental physics and applied engineering.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
