Scientists studying ‘magic-angle’ graphene have captured the clearest evidence yet of the electronic signature behind its superconductivity, cutting through years of speculation over what actually drives its exotic behaviour.

‘When superconductivity was first discovered in magic-angle graphene, it was surprising,’ says Jeong Min Park at Princeton University. ‘Graphene by itself was not a superconductor, yet simply twisting layers turned it into one.’

This is because when two or more graphene layers are twisted at a very specific angle – the magic angle – electrons in the system slow down dramatically. ‘When [this happens], they interact with each other much more strongly, and this gives rise to … new behaviours that don’t exist in the individual layers,’ says Park.

A standout feature of magic-angle graphene is its extreme tunability. ‘By applying small voltages nearby, a process called gating, you can turn the same device into a superconductor, an insulator or even a magnetic material,’ says Park. ‘One piece of magic-angle graphene behaves like thousands of different materials you can dial between.’

But this versatility comes at a cost: many electronic states lie close together, and their signals can overlap, making the desired electronic state hard to pinpoint. ‘This complexity is a big reason why its superconductivity has remained such an intriguing mystery,’ says Park.

To solve it, Park and collaborators from Pablo Jarillo-Herrero’s group at the Massachusetts Institute of Technology used a combination of tunnelling spectroscopy and transport measurements to provide direct evidence linking a specific electronic gap to magic-angle graphene’s superconducting state.

‘Each experimental technique revealed a different piece of the puzzle,’ she explains. ‘Transport measurements tell us when electricity flows without resistance, which is how we know the material has become superconducting… Tunnelling spectroscopy, on the other hand, shows the energy structure of the electrons directly, and allow us to potentially see the superconducting gap.’

They revealed the coexistence of two distinct energy scales: the first is a small, low-energy gap that disappears at a critical temperature and magnetic field, identifying it as the true superconducting gap. The second is a larger ‘pseudogap’, which Park speculates may signal a precursor state where electron pairs have formed up, but superconductivity hasn’t fully set in, or it reflects another electronic process that helps pave the way for superconductivity.

‘This observation fundamentally challenges the simpler, single-gap model,’ comments Antonio Castro Neto at the National University of Singapore, who was not involved in the study. ‘It provides the clearest evidence yet that superconductivity in this material is “unconventional”, likely involving electron pairs with a more complex structure.’

Beyond solving a long-standing mystery, the work lays the foundations for engineering quantum materials that could power future ultra-efficient quantum technologies. ‘Magic-angle graphene hosts a whole zoo of quantum phases,’ says Park. This makes it potentially useful for building quantum electronic circuits.

‘However, we are far away from practical applications,’ adds Castro Neto. ‘Major hurdles remain, including the extremely low operating temperature, material stability issues and limited current capacity. The value of this discovery is primarily in fundamental science.’