Decoding the Quantum Secrets of Graphene

A team of physicists from the Indian Institute of Science (IISc), Bangalore, in collaboration with researchers from Japan’s National Institute for Materials Science, has uncovered a remarkable quantum phenomenon in graphene, a single atomic layer of carbon atoms. This breakthrough demonstrates for the first time that electrons confined within an ultraclean graphene sheet can flow collectively as a nearly perfect, frictionless fluid. Their discovery not only challenges our fundamental understanding of electron transport in solid-state systems but also opens exciting avenues in quantum materials science, potentially revolutionizing electronic and thermal device technologies.

For decades, physicists have pondered whether electrons could ever behave like an ideal fluid—a state where they collectively move without scattering from impurities or lattice defects, giving rise to frictionless flow properties analogous to superfluids or quark-gluon plasmas. Conventional materials have continually thwarted efforts to observe such behavior due to imperfections that scatter electrons and mask the subtle hydrodynamic effects. However, graphene, with its distinct two-dimensional honeycomb lattice and exceptional electronic properties, has long been regarded as an ideal platform for exploring novel quantum states. Yet, direct evidence of hydrodynamic electron flow behaving as a perfect fluid has remained elusive—until now.

The IISc-led team meticulously prepared and engineered ultra-high-purity graphene samples, eliminating most extrinsic sources of disorder and defects. Using these pristine specimens, they simultaneously measured electrical conductivity—the ease with which electrons carry charge—and thermal conductivity, which reflects the ability of the material to transfer heat via electron motion. Surprisingly, rather than maintaining the well-established proportionality predicted by the Wiedemann-Franz law, their experiments revealed a striking inverse relationship. As the electrical conductivity increased, thermal conductivity decreased dramatically, breaking the long-held principle that heat and charge conductance should scale hand-in-hand in metals.

This profound violation of the Wiedemann-Franz law by more than two hundredfold at low temperatures signals the emergence of a unique quantum liquid regime. At the heart of this behavior is the so-called Dirac point, where graphene’s electronic band structure yields massless charge carriers and where electrons neither conform to metallic nor insulating states. Near this point, electrons abandon their typical particle-like individuality and instead coalesce into a collective “Dirac fluid.” This fluid flows similarly to water but displays quantum effects such as minimal viscosity—far lower than any classical fluid—thus qualifying it as the closest experimental realization of a perfect quantum fluid in a solid.

The researchers explain that, in the Dirac fluid regime, both charge and heat transport depend on a universal quantum of conductance—a fundamental constant describing the minimal resistance electrons experience when flowing across materials. This universality highlights the exotic nature of electron interactions within graphene, governed more by intrinsic quantum critical phenomena than by material-specific imperfections. Consequently, electrical and thermal conduction processes decouple fundamentally, invalidating traditional conductivity models that treat electrons as largely independent carriers.

To characterize the fluidity quantitatively, the team measured the fluid’s viscosity—a parameter indicating internal friction opposing flow. Their results revealed an extraordinarily low viscosity, on par with other strongly correlated quantum systems such as the quark-gluon plasma observed in ultra-high-energy collisions at CERN’s Large Hadron Collider. Such correspondence suggests that the graphene Dirac fluid can serve as a low-energy table-top analog to explore extreme quantum states usually accessible only in particle physics experiments and astrophysical scenarios.

Beyond its fundamental importance, this discovery positions graphene as an unparalleled quantum laboratory for investigating rich phenomena like black-hole thermodynamics and entanglement entropy scaling, concepts that historically belong to the realms of cosmology and quantum information theory. The ability to simulate and probe these exotic states in a controlled laboratory environment will undoubtedly accelerate progress across condensed matter physics and quantum technologies.

Technological implications of this research are equally profound. The emergence of a quantum perfect fluid phase in graphene paves the way for quantum sensors engineered to exploit the decoupling of charge and heat flows, granting these devices heightened sensitivity. Potential applications include amplification of weak electrical signals and detection of minute magnetic fields, advancing fields such as quantum metrology and medical imaging.

Professor Arindam Ghosh of IISc, one of the study’s senior authors, emphasizes the enduring richness of graphene’s physics despite two decades of intense scrutiny. “It is amazing that there is so much to do on just a single layer of graphene even after 20 years of discovery,” he notes, underscoring the material’s continual capacity to surprise and inspire.

First author Aniket Majumdar explains that this work marks a key milestone in realizing a Dirac fluid state experimentally. He points out that this unique electronic phase is “an exotic state of matter which mimics the quark-gluon plasma,” highlighting its importance in bridging condensed matter and high-energy physics. The study’s observation that electron flow near the Dirac point mimics such a nearly perfect fluid feeds into longstanding theoretical predictions regarding quantum criticality and hydrodynamic transport in two-dimensional materials.

The team’s approach involved precise tuning of graphene’s carrier density to reach the Dirac point through electrostatic gating techniques, enabling unprecedented control over the electron fluid’s properties. By cooling the samples to cryogenic temperatures, they suppressed extrinsic thermal scattering and unveiled intrinsic collective electron phenomena that remain hidden at higher energies.

Their findings demonstrate a new universality class of quantum critical flow, distinct from classical or previously known quantum transport regimes. This universality is characterized by the reliance on fundamental constants governing conductance rather than sample-specific parameters, reinforcing graphene’s status as a model system to study quantum fluids with direct experimental accessibility.

As a result, the IISc team’s breakthrough establishes a vibrant new frontier in quantum materials research. By taking quantum fluid dynamics out of particle accelerators and astrophysics labs and placing it squarely in a table-top graphene device, this study promises to reshape fundamental physics paradigms and to spark technological innovations exploiting quantum hydrodynamics in future nanoelectronic systems.

The research is published in the prestigious journal Nature Physics, amplifying its impact and signaling global recognition for this milestone achievement. This advance in understanding electron behavior at the quantum critical point in graphene not only enriches our fundamental knowledge of quantum many-body systems but also energizes diverse areas of physics—ranging from condensed matter to quantum information and high-energy theory.

As materials science continues to push boundaries, discoveries such as this spotlight the profound possibilities emerging from atomically thin materials. Graphene’s exceptional electron fluidity offers a glimpse into an extraordinary quantum world, where electrons flow as a near-perfect liquid, setting the stage for innovations that transcend conventional electronics and unveil unexplored quantum frontiers.

Subject of Research: Quantum fluid behavior of electrons in ultraclean graphene

Article Title: Universality in quantum critical flow of charge and heat in ultraclean graphene

News Publication Date: 13-Aug-2025

Web References:
https://www.nature.com/articles/s41567-025-02972-z
http://dx.doi.org/10.1038/s41567-025-02972-z

Image Credits: Aniket Majumdar

Keywords

Graphene, quantum fluid, Dirac fluid, electron hydrodynamics, quantum criticality, Wiedemann-Franz law violation, quantum conductance, minimal viscosity, quantum transport, graphene electronics, ultraclean graphene, quantum sensors

Tags: collective electron behaviorelectronic device technologiesfrictionless electron flowhydrodynamic electron transportIndian Institute of Science researchquantum materials sciencequantum properties of graphenesolid-state physics breakthroughssuperfluid-like propertiesthermal device innovationstwo-dimensional materials researchultraclean graphene sheets