Strange matter

UAlberta physicist spotlights "strange hybrids" for a prominent journal's review of recent research in condensed matter physics.

Suzette Chan - 22 September 2015

(Edmonton) The prestigious science journal, Nature Physics, recently published a progress article on condensed matter theory by University of Alberta Assistant Professor Joseph Maciejko.

A progress article is a short review article that surveys recent progress in a rapidly developing field. Maciejko, who is the Canada Research Chair for Condensed Matter Theory, wrote about fractionalized topological insulators, an idea that he, his co-author (Gregory A. Fiete of University of Texas, Austin), and other physicists around the world are researching.

While it's been established that most solids are usually either metals or insulators, a topological insulator is a strange hybrid between the two.

"A topological insulator is insulating, meaning that electricity cannot flow through its interior. However, electric currents can flow on its surface," Maciejko says. "While electrical conduction in ordinary metals is always accompanied by heat dissipation - as anyone who has ever held a hot laptop on their lap knows - electrical conduction on the surface of a topological insulator does not dissipate heat at all. This makes topological insulators particularly interesting for applications to low-power, energy-efficient electronics."

Meanwhile, electrons in a fractionalized topological insulator behave unusually. "The behaviour of a fractionalized topological insulator is best described by collective motions of large numbers of electrons, which acquire an identity of their own -- just like a tsunami is better described by a single wave than by a collection of water molecules."

Maciejko says that these collective motions - also known as quasiparticles - acquire strange properties, such as carrying exactly one-third of the charge of an electron. "These counterintuitive effects are a consequence of the laws of quantum mechanics, which electrons, like all subatomic particles, must obey."

The experimental search for a fractionalized topological insulator is currently ongoing. Physicists hypothesize that the phenomenon may occur in materials such as iridium compounds and systems of ultracold atoms in optical lattices.

Joseph Maciejko's progress report on research in this field can be found here: