As an ultra-thin, super-strong, ultra-soft and ultra-high-speed electrical conductor, graphene has been regarded as a magical material with a wide range of applications in the electronics field. But to make the most of the huge potential of graphene, scientists must first understand where the superpower of graphene comes from. According to a report by the Physicist Organization Network on August 3 (Beijing time), American scientists have taken the latest step in this direction: their research confirmed for the first time that the interaction between electrons in graphene is the key to the extraordinary performance of graphene. . Related papers have been published in the journal Nature and Physics.

Electrons can travel at a speed close to the speed of light in graphene, which is 100 times faster than the speed of electrons in silicon. Since the electrons in graphene behave like extreme relativistic free electrons without mass, and scientist Paul Dirac described the relativistic electronic behavior in 1928 using the Dirac equation, the charge carriers in graphene are also called It is the "Dirac quasiparticle", which is the massless Dirac fermion. Michael Cromi, a physicist at the University of California, Berkeley, who led the study, said: "The response of electrons in graphene to the Coulomb potential of charged impurities and the performance of non-relativistic electrons in traditional atom-immune systems should Very different. However, until now, many key theoretical predictions related to this extreme relativistic system have not been tested."

The team he led for the first time observed and recorded on the microscopic scale how electrons and holes in a gated graphene device respond to the Coulomb potential, thus "the interaction between electrons is the key to the extraordinary performance of graphene." The theory provides experimental support. They placed a boron nitride sheet on the most common Semiconductor-based silica substrate and then deposited a graphene layer on the sheet to make a gated device using ultra-high vacuum scanning tunneling microscopy (STM). Detection of the gated device. At the same time, they used the tip of the microscope to automatically manipulate the cobalt monomer to construct a cobalt trimer on the graphene sheet as a charged impurity for the Coulomb potential.

Ultra-high vacuum scanning tunneling microscopy shows the response of electrons and holes to the Coulomb potential by recording the spatial variation of the graphene electronic structure. Comparing the electron-hole asymmetry observed in the experiment with the theoretical simulation, the research team can not only verify the relevant theoretical predictions, but also find that the dielectric constant of graphene is small enough, which is the interaction between electrons. The evidence of the extraordinary performance of graphene is important for understanding how electrons in graphene move.

“Some researchers believe that the interaction between electrons and electrons is not important to the intrinsic properties of graphene, but other experts have the opposite view. We first used images to show how extreme relativistic electrons can realign themselves by coulombing themselves. The response responded that the interaction between electrons is an important factor in determining the performance of graphene," Cromi said.

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