Synopsis: Dirt and geometry insulate electrons

Random disorder in topological insulators leads to an insulating phase reminiscent of one known for years in two-dimensional systems.
Synopsis figure

Random disorder can render a two-dimensional system of noninteracting electrons into an insulating state known as the Anderson insulator [1]. Another well-known manifestation of two-dimensional physics—the integer quantum Hall effect—is the formation of dissipationless current-carrying edge states in the presence of a magnetic field.

Writing in Physical Review Letters, Jian Li, Rui-Lin Chu, and Shung-Qing Shen of The University of Hong Kong and Jainendra Jain of Pennsylvania State University in the US address how disorder affects edge states in topological insulators, a class of band insulators that exhibit strange conduction properties similar to what is seen in quantum Hall states, but in the absence of an external magnetic field. (See also the Viewpoint on topological insulators [2].)

It is known that the physics of topological insulators is immune to weak disorder. However, the authors also predict a surprising phase in HgTe/CdTe quantum well topological insulators. They call this phase the topological Anderson insulator, where disorder introduces two key differences from previously studied topological insulators: The Fermi energy lies in a so-called mobility gap, as opposed to a “real” gap, and the edge states do not appear to depend on the specific band structure of the quantum wells. That said, these HgTe/CdTe quantum wells possess an “inverted” band structure and offer the possibility to considerably tweak their transport and structure properties, which in turn promises further insights into how disorder and doping modify the phase diagram of topological insulators. – Sami Mitra

[1] E. Abrahams, Phys. Rev. Lett. 42, 673 (1979).

[2] S. C. Zhang, Physics 1, 6 (2008).


Announcements

More Announcements »

Subject Areas

Semiconductor PhysicsMesoscopics

Previous Synopsis

Mesoscopics

Fragile state

Read More »

Next Synopsis

Fluid Dynamics

Viscous pull

Read More »

Related Articles

Synopsis: A Single-Level Electron Turnstile
Mesoscopics

Synopsis: A Single-Level Electron Turnstile

A combination of a quantum dot and superconducting leads works as an electron turnstile, letting only one electron pass at a time through a single level in the dot. Read More »

Viewpoint: Kondo Physics in a Quantum Channel
Mesoscopics

Viewpoint: Kondo Physics in a Quantum Channel

Using a scanning gate microscope, researchers have shown that electron waves scattered from a quantum point contact carry the imprint of interactions with localized electron spins. Read More »

Viewpoint: Precise Layering of Organic Semiconductors
Semiconductor Physics

Viewpoint: Precise Layering of Organic Semiconductors

Researchers have fabricated high-quality organic semiconductors only a few molecular layers thick, revealing how the crystal structure affects the electronic properties. Read More »

More Articles