Synopsis: How Defects Keep Graphene Cool

Defects in graphene lead to a localized cooling effect that could be used to control heat dissipation in nanodevices.
Synopsis figure
J. F. Kong/MIT

Material imperfections, such as an atom out of place or a boundary between crystallites, usually reduce a material’s ability to dissipate heat. Now Jian Feng Kong at the Massachusetts Institute of Technology, Cambridge, and colleagues predict a mechanism via which impurity defects—foreign atoms—in graphene can instead increase heat dissipation. Analyzing the impact of such defects on the local emission of phonons by the electrons, the team found that the defects can act like a resonant cavity for phonons, amplifying phonon emission up to tenfold. This cooling mechanism could be turned on and off by an applied voltage, enabling controllable cooling in graphene-based nanodevices.

The heat dissipation mechanism discovered by Kong and colleagues takes advantage of a process analogous to the so-called Purcell effect—the enhanced emission of photons by an atom trapped in a resonant optical cavity. Here, instead of an atom in a cavity, an electron is trapped by a defect. When an electronic transition of the defect is resonant with the energy of the trapped electron, the electron emits phonons more efficiently. This enhanced emission facilitates heat dissipation in the region around the defect.

The team predicts that this cooling mechanism could be tuned by changing the graphene sheet’s Fermi energy, which determines the energy of the electrons that interact with the defect. This tuning could be achieved experimentally by applying a voltage to the material. The researchers say that this Purcell-like mechanism could explain recently measured heat-dissipation maps of graphene that indicate that electrons lose most of their energy around defects.

This research is published in Physical Review B.

–Katherine Wright

Katherine Wright is a Contributing Editor for Physics.


Features

More Features »

Announcements

More Announcements »

Subject Areas

GrapheneCondensed Matter PhysicsMaterials Science

Previous Synopsis

Atomic and Molecular Physics

Three-Body Problem Solved for 1D Boson Trio

Read More »

Next Synopsis

Related Articles

Focus: X-Ray Movie Reveals Origin of Metal Splashing
Materials Science

Focus: X-Ray Movie Reveals Origin of Metal Splashing

X-ray imaging of a manufacturing technique has captured the formation of molten metal projectiles that produce imperfections. Read More »

Synopsis: Mirror, Mirror—Which Coating is the Quietest of Them All
Gravitation

Synopsis: Mirror, Mirror—Which Coating is the Quietest of Them All

Gravitational-wave detectors may benefit from an alternative coating material that is less noisy at low temperatures than currently used materials. Read More »

Synopsis: Tuning an Atom’s Magnetic Field
Magnetism

Synopsis: Tuning an Atom’s Magnetic Field

Researchers modify the magnetic field of a single atom, demonstrating a potential way to store information in tiny devices of the future. Read More »

More Articles