Physicists at the Indian Institute of Science (IISc) have observed electrons moving through graphene as a nearly frictionless liquid, a discovery that contradicts a long-standing law of physics, according to ScienceDaily.
Working with collaborators from the National Institute for Materials Science in Japan, the team identified this elusive quantum state within a single layer of carbon atoms. The findings, published in Nature Physics, reveal a behavior that has been difficult to detect due to atomic defects and impurities in real-world materials.
By creating exceptionally clean graphene samples, the researchers measured how the material conducts electricity and heat. They found that as electrical conductivity increased, thermal conductivity dropped, a direct contradiction of the Wiedemann-Franz law.
This law states that heat and electrical conduction in metals should be proportional. The researchers observed deviations from this principle by more than 200 times at low temperatures.
A quantum fluid
At a specific state known as the 'Dirac point,' electrons stop acting as individual particles and begin moving collectively. This creates what scientists call a 'Dirac fluid,' which mimics the behavior of the quark-gluon plasma found in particle accelerators.
'It is amazing that there is so much to do on just a single layer of graphene even after 20 years of discovery,' said Arindam Ghosh, a professor at the IISc Department of Physics and a corresponding author of the study.
Aniket Majumdar, a PhD student and the study's first author, noted that the fluid's viscosity is extremely low. This makes the state one of the closest realizations of a perfect fluid ever observed in a laboratory.
Despite the breakdown of standard laws, the conduction follows a universal constant tied to the quantum of conductance. This suggests the behavior is not random but governed by fundamental quantum scales.
This discovery positions graphene as a platform for studying extreme physics, including black-hole thermodynamics and high-energy astrophysics. The presence of this Dirac fluid could also lead to the development of highly sensitive quantum sensors capable of detecting faint magnetic fields and weak electrical signals.
