MANHASSET, NY -- Research physicists at the University of California, Riverside have identified an insulating property of “bilayer graphene” (BLG) formed when two graphene sheets are stacked in a special manner.
Single layer graphene (SLG) is gapless, and cannot be completely turned off because regardless of the number of electrons on SLG, it always remains metallic and a conductor.
“This is terribly disadvantageous from an electronics point of view,” said Chun Ning (Jeanie) Lau, a member of UC Riverside’s Center for Nanoscale Science and Engineering, in a statement. “BLG suggests a promising route – trilayer graphene and tetralayer graphene, which are likely to have much larger energy gaps that can be used for digital and infrared technologies.”
The physicists report that when the number of electrons on the BLG sheet is close to 0, the material becomes insulating.
“BLG becomes insulating because its electrons spontaneously organize themselves when their number is small,” said Lau. Lau explained that a typical conductor has a huge number of electrons, which move around randomly. When BLG has only a few electrons the interactions cause the electrons to behave in an orderly manner.
Allan MacDonald, the Sid W. Richardson Foundation Regents Chair in the Department of Physics at The University of Texas at Austin and a coauthor on the research paper, noted that the research team has measured the mass of a new type of massive quantum particle that can be found only inside BLG crystals.
“The physics which gives these particles their mass is closely analogous to the physics which makes the mass of a proton inside an atomic nucleus very much larger than the mass of the quarks from which it is formed,” he said. MacDonald explained that the experiment the research team conducted was motivated by theoretical work which anticipated that new particles would emerge from the electron sea of a BLG crystal.
The physicists gave their experimental results in Nature Nanotechnology.
A graphene sheet (red) is suspended
between two electrodes.
The research was supported by grants from the National Science Foundation, Office of Naval Research, FENA Focus Center, and other agencies.