Since its discovery, superconductivity — a quantum state where electrons flow without generating heat — has revealed a wealth of novel quantum phenomena. However, there’s still much to explore in this field. Currently, physicists are investigating edge supercurrents in materials known as topological superconductors. These edge supercurrents, located at the boundaries of a crystal, are distinct because they don’t mix with the main supercurrents found deeper within the crystal.
“The boundary states are special,” said N. Phuan Ong, the Eugene Higgins Professor of Physics at Princeton University and the senior author of the paper. “As in the well-explored topological insulators, the electronic edge states are distinct from the states in the bulk. Research on edge supercurrents in topological superconductors is still in its infancy.”
The study of edge supercurrents could potentially add a new dimension to the study of superconductivity that may benefit future superconducting and quantum technologies. For a long time, though, evidence for edge supercurrents eluded scientists. It remained unobserved despite numerous searches.
In 2020, the Princeton team published evidence for edge supercurrents in molybdenum telluride (MoTe2), a topological semimetal that becomes a superconductor when cooled to temperatures below 100 milliKelvin, which is a tenth of a Kelvin above absolute zero. This material is a Weyl semimetal, named after physicist Herman Weyl who investigated theoretically the properties of electrons in high-energy physics in the limit when their mass is set to zero. Recent research in quantum materials has turned up “Weyl semimetals” in which the electrons mimic the behavior of Weyl electrons.
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