Research team finds bilayer graphene works as an insulator

Graphene, nature’s thinnest elastic material, is a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice. Because of graphene’s planar and chicken wire-like structure, sheets of it lend themselves well to stacking.

BLG is formed when two graphene sheets are stacked in a special manner. Like graphene, BLG has high current-carrying capacity, also known as high electron conductivity. The high current-carrying capacity results from the extremely high velocities that electrons can acquire in a graphene sheet.

When investigating BLG’s properties the researchers found that when the number of electrons on the BLG sheet is close to 0, the material becomes insulating (that is, it resists flow of electrical current) – a finding that has implications for the use of graphene as an electronic material in the semiconductor and electronics industries.

“ BLG之所以变得绝缘，是因为它的电子在数字很小时会自发地组织起来，”物理学和天文学副教授，研究论文的主要作者Chun Ning（Jeanie）Lau说。“电子没有随机移动，而是以有序的方式移动。这被称为物理学中的“自发对称性破坏”，这是一个非常重要的概念，因为这是相同的原理，即“赋予高能量物理学颗粒的质量”。

研究团队的一个重要发现是，随着磁场的增加，BLG中的固有“能量差距”生长。

Single layer graphene (SLG) is gapless, however, 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 Lau, a member of UC Riverside’s Center for Nanoscale Science and Engineering. “BLG, on the other hand, can in fact be turned off. Our research is in the initial phase, and, presently, the band gap is still too small for practical applications. What is tremendously exciting though is that this work 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. We already have begun working with these materials.”

新的量子粒子

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 team has measured the mass of a new type of massive quantum particle that can be found only inside BLG crystals.

他说：“使这些颗粒质量的物理学与物理学非常相似，物理学使原子核内部的质子质量比形成其形成的夸克的质量大得多。”“但是，我们团队的粒子是由电子制成的，而不是夸克。”

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 reported their experimental results in Nature Nanotechnology.