Researchers at the Ecole Polytechnique Fédérale de Lausanne and Freie Universität Berlin have discovered strong superconductivity in a newly identified structure known as a supermoiré lattice. This finding, detailed in a paper published in Nature Physics on February 15, 2026, opens new avenues for the creation of advanced quantum materials.
A supermoiré lattice is formed when two or more layers of graphene are stacked with slight twisting angles, which alters the electron movement within the material. The research team focused on a twisted trilayer graphene structure that presents overlapping moiré patterns, leading to unique electronic properties.
The project, led by senior author Mitali Banerjee, initially aimed to create a device with identical twist angles. However, during experimentation, student researcher Zekang Zhou discovered that the phase diagram of their device was fundamentally different from the anticipated results observed in magic-angle twisted trilayer graphene. “The phase diagram inspired us to pursue this system,” Banerjee stated, highlighting the unexpected discoveries made during the research.
The unique behavior observed when an electric field was applied in both directions prompted the emergence of a resistive state across various regions of the material. The findings indicated an unusual asymmetry in the device’s responses, suggesting complex interactions at play within the supermoiré lattice.
Exploring Superconductivity in Graphene
The primary goal of the study was to investigate whether robust superconductivity could arise in a twisted trilayer graphene system characterized by broken mirror symmetry. To achieve this, the researchers conducted low-temperature electrical transport measurements on their device. “We measured its electrical resistance while tuning two key parameters: the carrier density and the displacement field,” Banerjee explained.
A crucial indicator of superconductivity is a dramatic drop in electrical resistance, ideally approaching zero. In their measurements, the team did observe near-zero resistance, supporting the hypothesis that superconducting states were indeed present. Banerjee noted that temperature-dependent measurements confirmed this observation, revealing that the superconducting state was suppressed as temperatures increased.
The research team also identified strong nonlinear transport behavior, suggesting that the system transitions from a superconducting state to a normal state beyond a critical direct current. This critical current value was further influenced by the application of an out-of-plane magnetic field.
Implications for Quantum Materials
The findings indicate that superconducting states within the supermoiré lattice can withstand magnetic fields in a unique manner. Despite the lack of mirror symmetry—due to differing twist angles—the researchers confirmed the existence of robust superconducting regions characterized by distinct critical temperatures and magnetic fields.
“Brown-Zak oscillations,” which occur when electrons synchronize with a repeating lattice pattern under a magnetic field, were also observed in this study. These oscillations serve as evidence that the graphene layers form a supermoiré lattice, reinforcing the findings that superconductivity can persist even in systems where symmetry is broken.
Banerjee emphasized the broader implications of this study. “Our findings demonstrate that the interference between distinct moiré lattices constitutes a new degree of freedom,” she remarked. This discovery not only enhances understanding of quantum phases in graphene but also paves the way for the design of materials and devices with novel electronic properties.
The research team plans to further explore systems where moiré quasicrystals interact with supermoiré lattices, aiming to uncover the conditions necessary for stabilizing a supermoiré lattice within a complex multidimensional parameter space. Banerjee expressed enthusiasm for future studies, particularly in understanding the microscopic origins of superconductivity in their unique device.
As research in twisted graphene systems continues to advance, this groundbreaking study highlights the potential for developing innovative quantum technologies and materials, significantly impacting future applications in the field.
