Researchers from the Indian Institute of Science, Harvard University and the National Institute for Materials Science in Tsukuba, Japan, have observed in graphene an exotic state of matter known as the Dirac fluid – a nearly perfect quantum liquid where electrons flow collectively rather than as individual particles. This work addresses a long-standing question in quantum physics: can electrons behave like a frictionless fluid governed by universal constants rather than material imperfections?
Working with ultra-clean samples, the team found that near graphene’s Dirac point – a special electronic tipping point where the material is neither metallic nor insulating – electrical and thermal conductivities do not follow the conventional Wiedemann–Franz law, which links them directly. Instead, they vary inversely: improving charge flow comes at the expense of heat transport and vice versa.
This violation of textbook physics exceeds a factor of 200, revealing that charge and heat in the Dirac fluid are governed by a universal quantum of conductance. At the same time, the fluid shows viscosity strikingly close to the theoretical lower limit for quantum fluids, reminding researchers of the quark–gluon plasma once thought to exist only in extreme environments like particle accelerators.
These results, according to the team, not only establish graphene as the first material where such universal transport behavior can be detected in the laboratory but also position it as a powerful model system for fundamental physics. Concepts from high-energy and gravitational physics, such as black hole thermodynamics and entropy scaling, can now be explored on a desktop platform made of nothing more than a sheet of carbon.
Beyond fundamental science, the minimally viscous Dirac fluid in graphene could pave the way for advanced quantum sensors capable of amplifying faint electrical signals and detecting extremely weak magnetic fields.