A new study reports transport experiments in rhombohedral tetralayer and pentalayer graphene revealing a spectrum of clean-limit, magnetic-field-enhanced superconductivities in ultrahigh-quality carbon-based systems.

The experiments leverage gate-tunable strong correlations in rhombohedral multilayer graphene, enabling high material quality that supports enhanced field-tuned superconductivity and proximity-induced spin-orbit coupling effects.

Unlike conventional superconductivity, the researchers suggest electrons may pair with aligned spins, which could allow superconductivity to endure or even strengthen under magnetic fields.

This proposed spin-aligned pairing offers a possible mechanism for field-resilient superconductivity, but it requires further experimental and theoretical investigation to confirm.

Remarkably, certain superconducting states persist and even grow when exposed to magnetic fields, challenging the standard view that magnetism suppresses superconductivity.

The work received support from the U.S. Office of Naval Research and MIT.nano for device fabrication, with international collaboration including Basel, Florida State University, University of Florida, and the National Institute for Materials Science in Japan.

Proximity-induced spin-orbit coupling adds new superconducting states without introducing extra disorder, offering a route to multiple superconductors in this platform.

Lead author Junseok Seo and Long Ju emphasize that simple carbon materials can host multiple superconducting states when structurally tuned, highlighting new physics in widely available graphene.

The findings point toward potential advancements in topological superconductivity by combining magnetic-field effects with proximitized SOC while preserving ultrahigh material quality.

The study, published in Nature, identifies four distinct superconducting states in rhombohedral graphene as electrons are hole-doped, with three states persisting under fields up to about 9 tesla and one state strengthening under a perpendicular field.

The researchers acknowledge that the microscopic origins of the multiple, field-boosted superconducting states are not yet fully understood and call for further experimental and theoretical work.

Compared with Bernal bilayer graphene, the pentalayer system shows enhanced superconductivity under both out-of-plane and in-plane magnetic fields, aided by flatter band dispersion and lower required gate fields.