• Number 348  |
• October 17, 2011

Scientists detect unusual ‘quasiparticles’ in tri-layer graphene

By studying three layers of graphene — sheets of honeycomb-arrayed carbon atoms — stacked in a particular way, scientists at Brookhaven Lab have discovered a “little universe” populated by a new kind of “quasiparticles” — particle-like excitations of electric charge. Unlike massless photon-like quasiparticles in single-layer graphene, these new quasiparticles have mass, which depends on their energy (or velocity). In theory, these unique quasiparticles become infinitely massive at rest!

That  accumulation of mass at low energies means this trilayer graphene system, if magnetized by incorporating it into a heterostructure with magnetic material, could potentially generate a much larger density of spin-polarized charge carriers than single-layer graphene. That would make this tri-layer graphene very attractive for a new class of devices based on controlling not just electric charge but also spin, commonly known as spintronics.

“Our research shows that these very unusual quasiparticles, predicted by theory, actually exist in three-layer graphene, and that they govern properties such as how the material behaves in a magnetic field — a property that could be used to control graphene-based electronic devices,” said Brookhaven physicist Igor Zaliznyak, who led the research team. Their work measuring properties of tri-layer graphene as a first step toward engineering such devices was published online in Nature Physics on September 25, 2011.

[Karen McNulty Walsh, 631.344.8350,
kmcnulty@bnl.gov]