The Dirac point is the most recognizable feature of graphene’s electronic spectrum. The Dirac plasma has been found to exhibit unusual properties, including quantum-critical scattering and hydrodynamic flow. However, little is known about the plasma’s behavior in magnetic fields.
A study from scientists at The University of Manchester has discovered that good old graphene, which appeared to have been thoroughly investigated over the previous two decades, has a potent response, reaching above 100% in magnetic fields of typical permanent magnets (of approximately 1,000 Gauss). In terms of all available materials, this is a record of magnetoresistivity.
Scientists achieved this by using high-quality graphene. They tuned the graphene to its intrinsic, virgin state where there were only charge carriers excited by temperature. As a result, a plasma of quickly moving “Dirac fermions” was produced, which surprised researchers with its great mobility despite frequent scattering. The claimed giant magnetoresistance is mostly due to the Dirac plasma’s great mobility and neutrality.
In addition to the record magnetoresistivity, the researchers have discovered that neutral graphene transforms into a so-called “strange metal” at high temperatures. These materials are referred to as having fast electron scattering, which is solely determined by the Heisenberg uncertainty principle. Uncertainty surrounds the behavior of unusual metals, which is still being investigated globally.
Scientists noted, “This work adds some more mystery to the field by showing that graphene exhibits a giant linear magnetoresistance in fields above a few Tesla, which is weakly temperature dependent. This high-field magnetoresistance is again record-breaking.”
The study offers significant clues on the origins of the strange metal behavior and the linear magnetoresistance. Due to graphene, which is a clear, well-defined, and relatively simple electrical system, the puzzles may have finally been addressed.
Dr. Leonid Ponomarenko, from Lancaster University, said, “Undoped high-quality graphene at room temperature offers an opportunity to explore an entirely new regime that in principle could be discovered even a decade ago but somehow was overlooked by everyone. We plan to study this strange-metal regime and, surely, more interesting results, phenomena, and applications will follow.”