In a groundbreaking advancement from The Ohio State University, physicists have developed a novel method to precisely control superconductivity in twisted bilayer graphene (TBLG), a two-dimensional material poised to revolutionize electronics and quantum technologies. Led by Professor Chun Ning 'Jeanie' Lau, the research team demonstrated that by tuning the surrounding environment, they can switch superconducting states on and off with remarkable precision. This discovery, detailed in a study published on April 7, 2026, in Nature Physics, challenges conventional understanding and opens doors to practical applications long dreamed of in materials science.
The breakthrough centers on attaching TBLG to strontium titanate (SrTiO3), a substrate with a tunable dielectric constant. By adjusting electron interactions through this interface, the team observed suppression or enhancement of superconductivity, revealing the 'double-edged' role of interactions in pair formation. This environmentally sensitive control is unprecedented, as traditional superconductors respond differently to such tuning.
Foundations of Superconductivity: A Primer
Superconductivity, first discovered in 1911 by Heike Kamerlingh Onnes, is the phenomenon where certain materials conduct electricity with zero resistance when cooled below a critical temperature (Tc). This lossless flow arises from electrons forming Cooper pairs, overcoming their natural repulsion via lattice vibrations (phonons) in conventional cases or more exotic mechanisms in high-temperature superconductors.
High-temperature superconductors (HTS), operating above liquid nitrogen temperatures (~77 K), promise efficient power grids, maglev trains, and MRI machines without bulky cooling. However, controlling Tc and stability remains challenging. TBLG, 'magic angle' graphene twisted at ~1.1 degrees, emerged in 2018 as a HTS platform with Tc up to 1.7 K, exhibiting correlated insulating states and unconventional pairing.
Ohio State's prior work on TBLG laid groundwork, but this study introduces environmental tunability, a game-changer for device integration.
The Ohio State Team and Their Experimental Setup
Professor Jeanie Lau, a leading expert in 2D materials at OSU's Department of Physics, heads the Quantum Research Lab. With over 100 publications and awards like the APS Fellow, Lau's group excels in nanofabrication and low-temperature measurements. Lead author Xueshi Gao, a PhD candidate, drove the experiments, supported by co-authors Aatmaj Rajesh, Emilio Codecido, Daria Sharifi, Zheneng Zhang, Youwei Liu, and Marc Bockrath—all OSU affiliates. International collaborators include Alejandro Jimeno-Pozo, Pierre Pantaleon, Paco Guinea (IMDEA Nanoscience, Spain), Kenji Watanabe, and Takashi Taniguchi (Japan).
The setup: TBLG devices suspended 3-4 nm above bulk SrTiO3, enabling in situ dielectric tuning. Measurements at millikelvin temperatures used transport probes to map resistance vs. density and temperature, revealing the superconducting dome.
Step-by-Step: Tuning Superconductivity
The method unfolds as follows:
- Fabrication: Stack two graphene layers at magic angle (~1.1°), encapsulate in hexagonal boron nitride (hBN) for protection, and position atop SrTiO3.
- Environmental Sensitivity: SrTiO3's dielectric constant (ε) is tuned by gating or temperature, screening Coulomb interactions.
- Interaction Control: Increase ε to weaken electron repulsion; observe superconducting dome (Tc vs. carrier density).
- Observation: Higher ε suppresses dome height/width. In 1.4° TBLG (normally non-superconducting on SiO2), superconductivity emerges on SrTiO3 without insulators.
This reveals interactions mediate pairing via plasmons, e-h pairs, phonons—double-edged, as excess screening disrupts.
Surprising Discoveries: Unconventional Physics
Unlike Bardeen-Cooper-Schrieffer (BCS) theory, where screening aids pairing, here stronger screening weakens it. Theory models pairing from screened Coulomb repulsion, aligning with experiments. Large-angle TBLG shows superconductivity sans insulators, suggesting decoupled phenomena.
Lau notes: "Electrons' sensitivity to environment is unexpectedly important for material changes." Gao adds: "Our result sheds light on applying this to future work."
Implications for Quantum Technologies
This control promises tunable Josephson junctions for qubits, enhancing quantum computers. OSU's nanofab expertise positions it as a hub for quantum materials research. Funded by DOE/NSF, it underscores federal support for US higher ed innovation.
Statistics: Global quantum market $1T by 2035 (McKinsey); HTS could cut energy losses 10% in grids ($100B savings/year).
Quantum Computing and Beyond
Superconducting qubits (IBM, Google) need precise control; this method enables on-chip tuning, reducing decoherence. Potential: Fault-tolerant quantum devices, sensors detecting single photons/magnets.
Path to Room-Temperature Superconductors
HTS Tc ~130K (cuprates); TBLG hints at phonon-electron interplay scalable to higher Tc. Environmental tuning simplifies engineering, bypassing high-pressure needs (e.g., LK-99 controversy).
Challenges: Scaling fabrication, stability. OSU's cleanroom advances address this.
Ohio State's Role in Materials Science Excellence
OSU's Center for Superconducting and Magnetic Materials (CSMM) pioneers Nb3Sn wires for LHC upgrades. Lau's lab complements, focusing 2D systems. This elevates OSU's NIRF-like rankings in physics.
For students: OSU offers PhD/MS in Physics/Materials Science; research assistantships abound. Explore research jobs or faculty positions.
Stakeholder Perspectives and Broader Impacts
- Researchers: Enables new experiments on interaction-driven pairing.
- Industry: Partners like IBM could integrate for chips.
- Higher Ed: Boosts US competitiveness vs. China/EU quantum race.
- Society: Greener energy, medical imaging advances.
Expert quote: Guinea (IMDEA): "Highlights unconventional pairing mechanisms."
Photo by Olivia Anne Snyder on Unsplash
Future Directions and Open Questions
Next: Test other dielectrics, higher Tc materials, hybrid systems. Timeline: Prototypes in 5 years, commercial in 10+. OSU seeks collaborators; career opps in academic CV tips.
This Ohio State milestone exemplifies university-led innovation driving national progress.