Synopsis: Shaking Open a Gap in Graphene

To make graphene behave more like a semiconductor, researchers propose vibrating the lattice in a specific rotating pattern.

Graphene is an amazing material that has a lot going for it. But one thing it lacks is a gap in its electronic band structure that would allow it to be used as a semiconductor. Researchers can artificially introduce a gap, but often the energy separation is fixed. A new theoretical study in Physical Review Letters demonstrates how a special phonon excitation of graphene could open up a tunable gap in the material.

Graphene’s conductivity rivals that of most metals, but it is actually a zero-gap semiconductor, in which the conduction and valence bands meet at a single point. The missing gap could be advantageous for using graphene in solar cells, but it limits the use of the material in transistors. Doping or cutting graphene into nanoribbons can create a gap but may also, unfortunately, reduce the conductivity. Other techniques, like placing graphene sheets on a substrate, do not allow tuning of the gap.

Thomas Iadecola of Boston University, Massachusetts, and his colleagues have formulated a gap-opening mechanism that involves driving the carbon atoms away from their equilibrium positions. To do this, they imagine a phonon excitation (coming from, for example, inert atoms scattering off the material) that deforms the bond lengths in the lattice in a rotating pattern around the hexagonal structure. When they calculate the effect on the electrons, they find that the phonon-excited system is equivalent to an equilibrium state in which graphene has a band gap, whose width depends on the phonon amplitude. As a representative case, phonons that deform the bond lengths by 0.04% should produce a band gap of 0.025 electron volts. – Michael Schirber


More Features »


More Announcements »

Subject Areas


Previous Synopsis

Atomic and Molecular Physics

Remove the Noise

Read More »

Next Synopsis

Related Articles

Synopsis: Nonmetallic Tin Behaves Like 3D Graphene

Synopsis: Nonmetallic Tin Behaves Like 3D Graphene

By applying strain to a form of tin, researchers make it behave like a 3D analog of graphene. Read More »

Synopsis: Dirac Cones in Boron’s Version of Graphene
Materials Science

Synopsis: Dirac Cones in Boron’s Version of Graphene

A one-atom-thick sheet of boron atoms exhibits Dirac cones, marking the first time this electronic property has been found in a material lacking a graphene-like crystal structure.  Read More »

Synopsis: Graphene’s Elegant Optics Explained

Synopsis: Graphene’s Elegant Optics Explained

Theoretical calculations anchor graphene’s simple optical absorption in its two-dimensional structure instead of its cone-shaped energy bands. Read More »

More Articles