Groundbreaking research confirms the existence of edge supercurrents in topological superconductors, paving the way for the next generation of quantum technologies.
De-knotting the Braided Wavefunction
One such new class of materials where intriguing physics emerge from the characteristic topology of their wavefunction, are topological phases. Think about a substance where the electrons are influenced by an intertwined or wound wavefunction. When the stuff meets the surrounding space, the Wavefunction-wrapper must necessarily unwind and that means at edge there is a very rapid change.
The upshot is a creation of so-called ‘edge states’ where the electrons of the material edge exhibit different behavior than those inside the bulk. If the topological material is a superconductor, then the bulk and the edge are both superconducting but they do so in an unusual manner — much like two adjacent puddles of water that refuse to coalesce.
Decrypting the Mysteries of Edge Supercurrents
The new study, reported in the journal Nature Physics, focuses on edge supercurrents that flow along boundaries in the topological superconductor molybdenum telluride (MoTe2). In the presence of a magnetic field, however, supercurrent (injected current which can be injected without losing superconductivity) will oscillate in this material while passing an electrical charge. The edge supercurrent actually oscillates at a higher frequency than the bulk, in its own characteristic pattern that researchers can observe to track what the superconducting electrons are doing.
The researchers put a niobium (Nb) layer on top of MoTe2 to increase the ‘glue’ that holds the paired electrons together. The corresponding MoTe2 supercurrent oscillations are also boosted by this spill over as Nb has a larger pair potential. On the other hand, it also exposes an inconsistency between the Nb and MoTe2 pair potentials that cannot be continuously amalgamated. The edge electrons then have the ‘choice’ of either of the Nb and MoTe2 pair potentials, which is revealed in oscillations; for oscillation periods that differ between two materials (one from bulk, one from edge), higher frequencies lead to noisier oscillations.
Conclusion
While this may be the first report of edge supercurrents in topological superconductors, it shows that we can use these currents to learn how electrons in a superconductor behave. In theory, the knowledge could be turned into new quantum technologies — such as error-free quantum computers and energy-efficient electronics. This giant leap towards the extraordinary is a journey to discover the mysteries of topological superconductivity, marking the beginning of drawing ever nearer to a future where such things are just everyday normal bits and bobs.
