Synopsis: Same difference

A detailed investigation shows that the topological Anderson insulator phase is not distinct but part of the quantum spin-Hall phase.
Synopsis figure
Credit: E. Prodan, Phys. Rev. B (2011)

Suitably tuned mercury telluride/cadmium telluride quantum wells were predicted to be two-dimensional topological insulators and host the quantum spin-Hall effect, exhibiting chiral edge states that carry opposing spins in opposite directions. Experiments did verify that prediction, but the presence of disorder complicates the story. While the surface states of a topological insulator are immune to weak disorder, the experiments revealed hallmarks of localization. Concentrated efforts to understand this puzzle led to the discovery of the topological Anderson insulator, a state of matter in which disorder not only induces the well-known metal insulator transition but, in fact, is also responsible for topological nontriviality, i.e., the creation of the edge states. Intense debate ensued on whether this phase is fundamentally new and therefore disconnected from the quantum spin-Hall phase in the relevant phase space.

Now, in an article appearing in Physical Review B, Emil Prodan from Yeshiva University in New York settles the issue. By numerically exploring in detail the phase space characterizing these systems, Prodan shows that the topological Anderson insulator phase is not distinct but rather a part of the quantum Hall insulator phase, the boundaries of which become severely deformed as disorder is strengthened. This work provides a new way to understand the origin of the topological Anderson insulator phase. – Alex Klironomos


Announcements

More Announcements »

Subject Areas

Spintronics

Previous Synopsis

Next Synopsis

Semiconductor Physics

Guided by voltage

Read More »

Related Articles

Synopsis: Watching Spin Currents
Spintronics

Synopsis: Watching Spin Currents

X-ray pulses have been used to directly observe the spin current flowing in a metal. Read More »

Synopsis: How Spin Waves Bend
Spintronics

Synopsis: How Spin Waves Bend

Researchers have verified experimentally that the reflection and refraction of spin waves at an interface follow a Snell’s-like law. Read More »

Synopsis: Magnon Drag
Spintronics

Synopsis: Magnon Drag

Quantized spin waves known as magnons could experience a drag-like phenomenon in two spatially separated ferromagnetic layers. Read More »

More Articles