Researchers from Penn State, University of Oxford, Zhejiang University, Diamond Light Source and the University of North Texas have engineered an atomically confined gallium trilayer between graphene and silicon carbide that hosts robust Ising‑type superconductivity under strong in‑plane magnetic fields. This interface‑driven superconducting state in a light‑element heterostructure opens intriguing opportunities for integrating superconductivity with spin‑based functionalities in future spintronics devices.
The device consists of just three atomic layers of gallium sandwiched between a graphene overlayer and a 6H‑SiC(0001) substrate, grown using plasma‑free confinement epitaxy assisted by a carbon buffer layer. Within this ultra‑thin “quantum well,” superconductivity emerges at low temperatures, while the graphene capping layer protects the gallium from oxidation and contamination and the SiC substrate provides a structurally and electronically active interface. The result is a clean, strongly confined 2D superconducting channel whose properties are dominated by interfacial quantum interactions.
A key result is the emergence of interfacial Ising‑type superconductivity, where the spins of the Cooper pairs are locked perpendicular to the plane of the film. This spin locking makes the superconducting state remarkably resilient to in‑plane magnetic fields that would normally destroy Cooper pairs via the Pauli paramagnetic effect. Electrical transport measurements show that the in‑plane upper critical magnetic field reaches about 21.98 T at 400 mK, approximately 3.38 times the Pauli paramagnetic limit, placing this system well into the regime of strongly spin‑protected superconductivity that is of central interest for superconducting spintronics and high‑field quantum technologies.
To understand the microscopic mechanism behind this resilience, the team combined angle‑resolved photoemission spectroscopy with theoretical modeling. These studies reveal split Fermi surfaces with Ising‑type spin textures at the K and K′ valleys of the confined gallium layer. The spin textures arise from strong atomic‑orbital hybridization between the gallium layer and the SiC substrate, which induces effective spin–orbit coupling and breaks inversion symmetry at the interface. In other words, the spin structure that protects superconductivity is not an intrinsic property of a heavy element, but is engineered by the interface - a design principle that is highly relevant for spintronics, where control of spin-orbit coupling and spin textures at interfaces is a central theme.
This work demonstrates that Ising‑type superconductivity - and the associated robustness of Cooper‑pair spin polarization - can be realized in heterostructures built from relatively light elements by judicious interface and confinement engineering. Such superconductors can, in principle, serve as spin‑robust superconducting electrodes, building blocks for devices exploring spin-supercurrent conversion, or platforms for interfacing superconductivity with spin‑orbit‑coupled normal or magnetic layers. The ability to exceed the Pauli limit by more than a factor of three suggests that these interfaces could remain superconducting in magnetic fields compatible with many spin manipulation schemes, an essential requirement for practical superconducting spintronics.
Beyond this specific graphene/gallium/SiC stack, the authors highlight that their approach - combining quantum confinement with interfacial hybridization to engineer spin–orbit coupling and spin textures - constitutes a general design strategy. They aim to extend it to other light‑element metals such as indium and tin on suitable substrates, with the goal of building a broader family of interface‑engineered superconductors. For the spintronics community, this suggests a roadmap where superconducting and spin functionalities are co‑designed at the interface level, enabling devices that exploit both dissipationless charge transport and controllable spin degrees of freedom in atomically precise heterostructures.