Quantum Liquid of Electrons in Graphene: A Scientific Breakthrough

In a remarkable scientific development, researchers from the Department of Physics at the Indian Institute of Science, in collaboration with colleagues from the National Institute for Materials Science in Japan, have unveiled the quantum liquid of electrons in graphene, a material composed of a single layer of pure carbon atoms. These findings, published in Nature Physics, open a new window into the quantum world and demonstrate that graphene is a unique laboratory for studying unprecedented quantum phenomena.

Graphene: The Material of the Future

Since its discovery two decades ago, graphene has continued to captivate researchers and scientists worldwide. As a material consisting of a single layer of carbon atoms, it possesses unique physical and chemical properties. Professor Arindam Ghosh, one of the study’s lead authors, expressed his amazement, stating, “It’s astonishing that there is still so much to discover in just a single layer of graphene even after two decades since its discovery.”

Graphene’s ability to conduct electricity and heat simultaneously is one of its most notable features. However, the research team discovered an inverse relationship between these properties, where electrical conductivity increases at the expense of thermal conductivity and vice versa. This discovery challenges the traditional Wiedemann-Franz law in metals, which states that the two values should be directly proportional.

Deviation from Traditional Physical Laws

In the samples prepared by the Indian Institute of Science team, researchers observed a significant deviation from the Wiedemann-Franz law, with the ratio exceeding 200 at low temperatures. This deviation highlights the decoupling of charge and heat conduction mechanisms, yet this phenomenon is not random. Both charge and heat conduction in this case depend on a universal constant independent of the material, equivalent to the quantum of conductance, a fundamental value related to electron motion.

This strange behavior occurs at the “Dirac point,” a precise electronic transition point achieved by adjusting the number of electrons in the material, where graphene is neither metallic nor insulating. In this state, electrons cease to behave as individual particles and move together as if they were a liquid, much like water but a hundred times less viscous.

Dirac Liquids: Similarity to Quark-Gluon Plasma

This water-like behavior near the Dirac point is referred to as a Dirac liquid, a peculiar state of matter that mimics quark-gluon plasma, a high-energy subatomic particle soup observed in particle accelerators at CERN. The team measured the viscosity of this Dirac liquid and found it to be very low, close to that of an ideal liquid.

Technological Applications and Scientific Research

These discoveries confirm that graphene is an ideal and cost-effective platform for studying high-energy physics concepts and space science, such as black hole thermodynamics and entanglement entropy scale, in a laboratory setting.

From a technological standpoint, the presence of Dirac liquid in graphene holds significant potential for use in quantum sensors capable of amplifying very weak electrical signals and detecting extremely weak magnetic fields.

Conclusion

In conclusion, with its scientific revolution and unique capabilities in conducting electricity and heat, graphene represents a unique quantum liquid that opens new horizons in the world of quantum physics. By deviating from traditional physical laws and proving the existence of Dirac liquid, graphene reinforces its role as an advanced research laboratory where scientists explore complex cosmic phenomena. It also represents a promising future for advanced technological applications, making it an essential material for future studies and technological innovations.