Physicists at the University of Michigan (U-M) and several other universities have discovered or confirmed several properties of the compound samarium hexaboride (SmB6) at low temperature that raise hopes for finding the “silicon” of the quantum era.

In an open-access paper in the journal Science, the U-M researchers say they provide the first direct evidence that samarium hexaboride (SmB6) is a “topological insulator” — a class of solids that are believed to conduct electricity like a metal across their surface, but block the flow of current through their interior.

The U-M scientists used a technique called torque magnetometry to observe tell-tale oscillations in the material’s response to a magnetic field that reveal how electric current moves through it.

Nature News notes that “SmB₆ is an unusual topological insulator because the electrons in the outer shells of the samarium atoms interact with one another strongly, such that a coordinated motion emerges. This could make the material useful for creating some exotic quantum effects, including magnetic monopoles, or Majorana fermions — quasiparticles that might be useful for quantum computing, says Shoucheng Zhang, who has pioneered work on topological insulators at Stanford University in California.”

This deeper understanding of samarium hexaboride raises the possibility that engineers might one day route the flow of electric current in quantum computers like they do on silicon in conventional electronics, said Lu Li, assistant professor of physics in the College of Literature, Science, and the Arts and a co-author of a paper on the findings published in Science.

Dirac electrons, named after the English physicist whose equations describe their behavior, straddle the realms of classical and quantum physics, Li said.

The U-M research was funded by the U.S. Department of Energy and the National Science Foundation. The U-M Mcubed program also provided seed funds for this research.

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Abstract of Two-dimensional Fermi surfaces in Kondo insulator SmB6

In the Kondo insulator samarium hexaboride (SmB₆), strong correlation and band hybridization lead to an insulating gap and a diverging resistance at low temperature. The resistance divergence ends at about 3 kelvin, a behavior that may arise from surface conductance. We used torque magnetometry to resolve the Fermi surface topology in this material. The observed oscillation patterns reveal two Fermi surfaces on the (100) surface plane and one Fermi surface on the (101) surface plane. The measured Fermi surface cross sections scale as the inverse cosine function of the magnetic field tilt angles, which demonstrates the two-dimensional nature of the conducting electronic states of SmB₆.